USPS Flat Rate Box Rates 2026
Small Flat Rate Box $14.65, Medium $25.80, Large $36.10 at the Post Office, effective October 4, 2026. Below: USPS commercial pricing on every box, all four box dimensions, and the weight and zone where a Flat Rate box stops winning.
- $14.65Small Flat Rate Box at retail
- $25.80Medium box, either shape
- 70 lbsAny weight, any zone, one price
USPS Flat Rate Box
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Create a labelPrint a Medium Flat Rate Box label: $20.28 Pro price
Create a labelPrint a Large Flat Rate Box label: $28.06 Pro price
Create a labelA USPS Priority Mail Flat Rate box costs $14.65 for the Small box, $25.80 for either Medium box, and $36.10 for the Large box at retail, effective October 4, 2026.
These are USPS temporary holiday prices, in effect October 4, 2026 until January 17, 2027. USPS commercial pricing on those same boxes is about $12.95, $22.02, and $32.75. A USPS Flat Rate box ships any weight up to 70 lbs to any zone for that one price, delivers in 2 to 3 days, and includes tracking and $100 of insurance.
The box sizes are Small at 8.625 by 5.375 by 1.625 inches, Medium top-loading at 11 by 8.5 by 5.5 inches, Medium side-loading at 13.625 by 11.875 by 3.375 inches, and Large at 12 by 11.75 by 5.5 inches inside, and USPS supplies every one of them at no cost. The mistake that costs money is treating the Flat Rate box as the default.
Flat Rate only beats weight-based USPS Priority Mail when the parcel is heavy enough or the zone is far enough to overtake the fixed price, so a light box going to a nearby zone is usually cheaper priced by weight.
The temporary April 26, 2026 USPS increase raised Flat Rate prices about 8 percent, on top of the January 18 increase, and the temporary holiday prices from October 4 added to it again, which moved that break-even further out. A free I'd Ship That account prints discounted USPS and UPS labels, with USPS below commercial pricing on almost every label, with the full price shown before you buy.
The USPS prices on this page are USPS's temporary holiday prices, in effect from October 4, 2026 until January 17, 2027.
The I'd Ship That prices on this page are the ones the app shows on its current rate card; USPS's holiday increase does not add to them.
| Flat Rate item | Retail | Commercial |
|---|---|---|
| Flat Rate Envelopes (regular, legal, padded) | +$1.00 | +$0.85 |
| Small Flat Rate Box | +$1.00 | +$0.85 |
| Medium Flat Rate Boxes | +$1.00 | +$0.85 |
| Large Flat Rate Box, including APO/FPO | +$2.10 | +$1.75 |
Source: USPS announcement, August 25, 2026 and USPS Notice 123, effective October 4, 2026. See all 2026 USPS price changes.
Flat Rate is one of two ways to price Priority Mail. The other bills by weight and zone, and for a parcel under 3 to 4 lbs going to a nearby zone it is usually the cheaper of the two, so compare the box against the USPS Priority Mail rates by zone and weight before you pack.
On This Page
What USPS Flat Rate Box Includes at No Extra Cost#
USPS Flat Rate Box Prices by Size, 2026#
Every zone column on a USPS Flat Rate box holds the same number, which is the whole point of the product and also the trap: a Small Flat Rate Box costs $14.65 at retail whether it travels one county or one coast to the other, effective October 4, 2026.
USPS commercial pricing brings the Small box to about $12.95, the Medium box from $25.80 to about $22.02, and the Large box from $36.10 to about $32.75. On the Medium box that published gap is about $3.78 per package, and I'd Ship That prints below commercial on almost every label, so the gap against the counter is at least that wide.
Ship 20 Medium boxes a week at that gap and it is roughly $76 a week, about $3,931 over a year, on the same box and the same 2 to 3 day service. The volume figures are illustrative; the per-box gap is not.
| Container | Zone 1-4 | Zone 5-6 | Zone 7-8 | USPS Commercial |
|---|---|---|---|---|
| Flat Rate Envelope | $13.90 | $13.90 | $13.90 | $11.97 |
| Legal Flat Rate Envelope | $14.25 | $14.25 | $14.25 | $12.51 |
| Padded Flat Rate Envelope | $15.00 | $15.00 | $15.00 | $12.84 |
| Small Flat Rate Box (8.625x5.375x1.625) | $14.65 | $14.65 | $14.65 | $12.95 |
| Medium Flat Rate Box (11x8.5x5.5) | $25.80 | $25.80 | $25.80 | $22.02 |
| Medium Flat Rate Box (13.625x11.875x3.375) | $25.80 | $25.80 | $25.80 | $22.02 |
| Large Flat Rate Box (12x11.75x5.5) | $36.10 | $36.10 | $36.10 | $32.75 |
| APO/FPO Large Flat Rate Box | $34.65 | $34.65 | $34.65 | $31.34 |
$14.65 retail, about $12.95 commercial#
The Small Flat Rate Box measures 8.625 by 5.375 by 1.625 inches, roughly the footprint of a paperback and about an inch and a half deep. Anything that closes flat in it should not be going in a Medium.
- The step from Small to Medium is about $11.15 at retail, the largest jump in the lineup.
- Measure the item before you reach for a box, and repack when it fits.
- USPS supplies every Flat Rate shape at no cost from usps.com/supplies.
$25.80 retail either shape#
Both Medium boxes cost the same, so the choice is geometry, not price: an 11 by 8.5 by 5.5 inch top-loading cube and a 13.625 by 11.875 by 3.375 inch side-loading flat. USPS commercial pricing on either is about $22.02.
- The side-loading flat suits framed art, apparel, and anything wide and shallow.
- The top-loading cube suits stacked or bulky goods.
- Retail against commercial is about $3.78 per package on the same box and the same service.
Price it by weight instead#
Flat Rate is only ever a bet against weight-based pricing. Below the corner where both weight and zone are high, the fixed price is a premium paid for convenience. The 2026 increases pushed that corner further out.
- Under 3 to 4 lbs staying in nearby zones, weight-based USPS Priority Mail is usually cheaper.
- For a small dense box under 0.5 cubic feet, add Priority Mail Cubic to the comparison.
- Over 5 lbs heading to zones 5 through 8, the Medium box at $25.80 retail usually wins.
- Re-test the rule after every USPS price change, because a Flat Rate increase moves the break-even up.
Use the $34.65 Large box#
The APO/FPO Large Flat Rate Box is $34.65 at retail and about $31.34 commercial, against $36.10 retail for the standard Large box of the same 12 by 11.75 by 5.5 inch shape.
- Same 70 lb ceiling and same 2 to 3 day window.
- Tracking and $100 of insurance are included, as on every Flat Rate product.
- Set it as the default for military addresses rather than deciding per order.
When USPS Flat Rate Box Is the Right Service#
- Heavy, compact items that fit a Small or Medium Flat Rate box
- Cross-country shipments to zones 7 and 8, where weight-based rates climb hardest
- Sellers who want one predictable price per box instead of quoting every order
- Items over 5 lbs going long distances
- Military APO, FPO, and DPO addresses
- Dense goods like tools, books, and hardware that outrun their box size
USPS Flat Rate Box: What Experienced Shippers Do Differently#
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A USPS Flat Rate box only beats weight-based USPS Priority Mail on heavy parcels or far zones, so quote both before you buy rather than reaching for the box by reflex.
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Order USPS Flat Rate boxes delivered to your door at no cost at usps.com/supplies.
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The Medium Flat Rate Box comes in two shapes at the same $25.80 retail price, an 11 by 8.5 by 5.5 inch cube and a 13.625 by 11.875 by 3.375 inch flat, so pick the one that fits the item without crushing it.
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For items under 3 to 4 lbs staying in nearby zones, weight-based USPS Priority Mail is usually cheaper than any USPS Flat Rate box.
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For a small, dense parcel under 0.5 cubic feet, price Priority Mail Cubic against the Flat Rate box; Cubic bills by outside volume and frequently undercuts the Medium box.
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The APO/FPO Large Flat Rate Box is $34.65 at retail against $36.10 for the standard Large box, so use it on military addresses.
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Do not compare Flat Rate against weight-based by hand on every order. Ship Intelligence, a Pro feature, checks the cheapest valid rate and shows the savings.
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Shipping the same product repeatedly? Save a package preset with the box size and weight so every label is one tap, not a re-entry.
USPS Flat Rate Box: Key Takeaways#
- A USPS Flat Rate box costs $14.65 Small, $25.80 Medium, and $36.10 Large at retail, effective October 4, 2026, with USPS commercial pricing at about $12.95, $22.02, and $32.75.
- Flat Rate box dimensions are Small 8.625 by 5.375 by 1.625 inches, Medium 11 by 8.5 by 5.5 or 13.625 by 11.875 by 3.375 inches, and Large 12 by 11.75 by 5.5 inches, all supplied by USPS at no cost.
- A USPS Flat Rate box only beats weight-based USPS Priority Mail on heavy parcels or far zones; under 3 to 4 lbs to a nearby zone, weight-based pricing usually wins.
- The temporary April 26, 2026 USPS increase raised Flat Rate prices about 8 percent, which pushed the Flat Rate break-even further out than it was earlier in 2026.
- On a Medium Flat Rate Box, retail versus commercial pricing is about $3.78 per package on the same box and the same 2 to 3 day service.
When a USPS Flat Rate Box Costs More Than Weight-Based#
Where the box beats weight-priced Priority Mail
Small Flat Rate Box at $12.95 USPS commercial. Cells show Priority Mail commercial by weight; filled where the box is cheaper. USPS Notice 123, effective October 4, 2026.
Medium Flat Rate Box at $22.02 USPS commercial. Cells show Priority Mail commercial by weight; filled where the box is cheaper. USPS Notice 123, effective October 4, 2026.
Large Flat Rate Box at $32.75 USPS commercial. Cells show Priority Mail commercial by weight; filled where the box is cheaper. USPS Notice 123, effective October 4, 2026.
Medium Flat Rate Box at $20.28 through I'd Ship That, the Pro price. Cells show Priority Mail by weight at I'd Ship That's Pro price (1 to 20 lb); filled where the box is cheaper. I'd Ship That Pro prices, merchant rate card of October 18, 2026.
A USPS Flat Rate box is a fixed price, so its value depends entirely on what the weight-based alternative would have cost. Weight-based USPS Priority Mail rises with both weight and zone, which means the Flat Rate box wins in exactly the corner where both are high: a heavy parcel travelling far. Below that corner the fixed price is simply a premium you paid for convenience.
The rough rule that holds at the prices in force from October 4, 2026 is this. Under 3 to 4 lbs staying in nearby zones, quote weight-based USPS Priority Mail first. Over 5 lbs heading to zones 5 through 8, the Medium Flat Rate Box at $25.80 retail, about $22.02 commercial, usually wins. Between those two, quote both, because that band is where the answer flips and where the 2026 increases moved the line.
- Pull last month's labels and mark every Flat Rate box that went to zones 1 through 4 under 4 lbs; those are the ones that likely overpaid.
- Write the switching rule down and post it at the packing station: over 5 lbs to zones 5 through 8 goes Flat Rate, under 4 lbs to nearby zones goes weight-based.
- Re-test the rule after every USPS price change, because a Flat Rate increase moves the break-even weight up.
- For a small, dense box under 0.5 cubic feet, add Priority Mail Cubic to the comparison before you commit to Flat Rate.
USPS Flat Rate Box Sizes, Dimensions, and What Fits#
USPS Flat Rate boxes come in four shapes and three envelope styles, and picking the smallest one that closes flat is the whole optimization, because the price steps up sharply between sizes. The Small Flat Rate Box is 8.625 by 5.375 by 1.625 inches at $14.65 retail. Either Medium Flat Rate Box costs $25.80 retail: the top-loading cube at 11 by 8.5 by 5.5 inches and the side-loading flat at 13.625 by 11.875 by 3.375 inches. The Large Flat Rate Box is 12 by 11.75 by 5.5 inches at $36.10.
The jump from Small to Medium is about $11.15 at retail, which is the single largest step in the lineup, so a parcel that can be repacked into the Small box is worth repacking. The two Medium shapes cost the same, so choose by geometry rather than price: the side-loading 13.625 by 11.875 by 3.375 inch box suits framed art, apparel, and anything wide and shallow, while the top-loading cube suits stacked or bulky goods. Military addresses get their own Large box at $34.65 retail, cheaper than the standard Large.
- Measure the item before you pick a box; anything that fits 8.625 by 5.375 by 1.625 inches saves about $11.15 at retail against the Medium.
- Choose between the two Medium shapes by item geometry, not price, because both are $25.80 retail.
- Use the APO/FPO Large Flat Rate Box at $34.65 retail for military addresses instead of the $36.10 standard Large.
- Order boxes at no cost from usps.com/supplies so box choice is never limited by what is on the shelf.
Why the 2026 Increases Moved the Flat Rate Box Break-Even#
USPS raised prices three times in 2026. The first two, on January 18 and with a temporary 8 percent from April 26, lifted Flat Rate more steeply than the light end of the weight-based curve: the Medium box went from $21.05 to $24.80 across the two, while 1 lb Priority Mail to Zone 1 went from $10.05 to $11.00.
Temporary holiday pricing from October 4, 2026 until January 17, 2027 then added $1.00 to the Medium box ($25.80) and $0.50 to that 1 lb Zone 1 label ($11.50). That matters because Flat Rate is only ever a bet against weight-based pricing. When the fixed price rises faster than the variable one, the weight and zone at which the box starts winning moves further out, and a rule written in early 2026 now sends parcels to Flat Rate that would price lower by weight.
The practical response is a one-time re-test rather than an ongoing project. Take your three most common parcel profiles, quote each one as a Flat Rate box and as weight-based USPS Priority Mail at the current October 4, 2026 prices, and rewrite the switching rule from those six numbers. Once the rule is current, Ship Intelligence can enforce it automatically on every order and The Workbench can apply it across a whole batch import.
- Re-quote your three most common parcel profiles both ways at October 4, 2026 prices and rewrite the switching rule.
- Track average cost per label by service so a stale rule shows up as a rising number rather than a surprise.
- Buy below commercial pricing on almost every package so the increase lands nearer USPS's $22.02 commercial figure for a Medium box than the $25.80 counter price.
- Once you pass a few dozen labels a week, let Ship Intelligence enforce the rule and use The Workbench to batch-print.
Common Mistakes When Buying USPS Flat Rate Box Labels#
| Mistake | Why It Hurts | Better Approach |
|---|---|---|
| Reaching for a Flat Rate box on a light parcel going to a nearby zone | A 2 lb parcel to zone 2 in a Medium Flat Rate Box costs $25.80 at retail when weight-based USPS Priority Mail would have priced it far lower, and the reflex repeats on every similar order. | Quote weight-based USPS Priority Mail first on anything under 3 to 4 lbs staying in zones 1 through 4. |
| Using a Medium Flat Rate Box for something that fits the Small box | The step from $14.65 to $25.80 at retail is about $11.15 per package, the largest price jump in the Flat Rate lineup. | Measure the item against 8.625 by 5.375 by 1.625 inches before you pick a box, and repack when it fits. |
| Paying retail counter prices on Flat Rate boxes | A Medium Flat Rate Box is $25.80 at the counter against about $22.02 at USPS commercial pricing, about $3.78 per package on the same box. | Buy through a free I'd Ship That account so your full price, below commercial on almost every label, shows before you commit. |
| Running a Flat Rate switching rule written before April 26, 2026 | Flat Rate prices rose sharply in that change, so a rule set earlier in 2026 now routes parcels to Flat Rate that would price lower by weight. | Re-quote your three most common parcel profiles both ways at current prices and rewrite the rule. |
| Re-entering the same box and weight on every order | Lost time at scale and a higher chance of a wrong box choice that costs several dollars. | Save package presets, and move repeat batches into The Workbench for bulk import and batch-print. |
USPS Flat Rate Box Cost Control Checklist#
- Write down which orders default to a USPS Flat Rate box (suggested: over 5 lbs to zones 5 through 8).
- Set the fallback to weight-based USPS Priority Mail for light parcels staying in nearby zones.
- Measure your top three items against the Small box at 8.625 by 5.375 by 1.625 inches before defaulting to Medium.
- Check the live price in the app before buying instead of trusting the retail counter figure.
- Add Priority Mail Cubic to the comparison on any small, dense box under 0.5 cubic feet.
- Use the APO/FPO Large Flat Rate Box at $34.65 for military addresses.
- Re-quote your Flat Rate break-even against the October 4, 2026 USPS prices.
- Once you pass a few dozen labels a week, turn on Ship Intelligence and batch with The Workbench.
Worked USPS Flat Rate Box Shipment Examples#
Heavy for its size and travelling as far as domestic mail goes. This is the corner where a fixed price actually beats the weight-based curve.
- A Medium Flat Rate Box is $25.80 at retail and about $22.02 at USPS commercial pricing, whatever the zone.
- The same box would cost the same to the next county, which is the trade you are accepting.
- It ships up to 70 lbs in 2 to 3 days with tracking and $100 of insurance.
The reflex reach for a Flat Rate box on a light near-zone order, repeated on every similar shipment.
- The Medium box charges $25.80 at retail no matter how little the parcel weighs.
- Weight-based USPS Priority Mail would have priced this one far lower.
- The fix is a written rule: under 4 lbs to zones 1 through 4, quote by weight first.
One box size too big is the most expensive habit in the Flat Rate lineup, and it costs the same every time.
- $14.65 against $25.80 at retail is about $11.15 per package.
- The test is whether the item closes flat in 8.625 by 5.375 by 1.625 inches.
- At USPS commercial pricing the same step is about $12.95 against about $22.02.
USPS Flat Rate Box Questions Shippers Actually Ask#
USPS Flat Rate box retail prices are $14.65 for the Small box, $25.80 for either Medium box, and $36.10 for the Large box, effective October 4, 2026. Commercial pricing on the same boxes is about $12.95, $22.02, and $32.75. Those retail figures carry the temporary April 26, 2026 increase and the temporary holiday increase of October 4, 2026, so any Flat Rate box price published before October 4 is now low.
USPS Flat Rate boxes come in four shapes: Small at 8.625 by 5.375 by 1.625 inches, Medium top-loading at 11 by 8.5 by 5.5 inches, Medium side-loading at 13.625 by 11.875 by 3.375 inches, and Large at 12 by 11.75 by 5.5 inches. There are also Flat Rate Envelopes, Legal Flat Rate Envelopes, and Padded Flat Rate Envelopes. USPS supplies all of them at no cost.
A Medium Flat Rate Box costs $25.80 at retail and about $22.02 at USPS commercial pricing, effective October 4, 2026. Both Medium shapes cost the same: the top-loading box at 11 by 8.5 by 5.5 inches and the side-loading box at 13.625 by 11.875 by 3.375 inches. Either ships up to 70 lbs to any zone in 2 to 3 days with tracking and $100 of insurance.
A Large Flat Rate Box costs $36.10 at retail and about $32.75 at USPS commercial pricing, effective October 4, 2026. The box measures 12 by 11.75 by 5.5 inches inside. The APO/FPO version of the Large Flat Rate Box is cheaper at $34.65 retail and about $31.34 commercial, and it is the right choice for military addresses.
A Small Flat Rate Box costs $14.65 at retail and about $12.95 at USPS commercial pricing, effective October 4, 2026. The box measures 8.625 by 5.375 by 1.625 inches, which is roughly the footprint of a paperback and about an inch and a half deep. It ships up to 70 lbs to any zone, though weight rarely becomes the limit in a box that shallow.
No. A USPS Flat Rate box is cheaper only for heavier packages or shipments to distant zones 5 through 8. For items under 3 to 4 lbs staying in nearby zones, weight-based USPS Priority Mail is almost always less expensive. The temporary April 26, 2026 increase raised Flat Rate prices about 8 percent on top of January's, which pushed that break-even further out, so quote both before you buy.
No. USPS Flat Rate pricing requires an official USPS Flat Rate box or envelope. Order them at no cost at usps.com/supplies or pick them up at any Post Office. A shipment in your own packaging is rated as regular weight-based USPS Priority Mail instead, which on a light near-zone parcel is often the cheaper outcome anyway.
A USPS Flat Rate box holds up to 70 lbs, the same domestic limit that applies across USPS package services. In practice the box volume runs out long before the weight limit does on everything but dense goods like tools, hardware, and books. If the contents exceed 70 lbs or will not close the box flat, Flat Rate is not an option.
USPS raised Flat Rate prices three times in 2026: on January 18 (the Medium box from $21.05 to $22.95), with the temporary 8 percent from April 26 (to $24.80), and with temporary holiday pricing from October 4 until January 17, 2027 (to $25.80), enough to move its break-even against weight-based pricing. A shop sending 30 packages a week absorbs that on roughly 1,560 labels a year. Buying at below commercial pricing on almost every label puts the increase on a lower base.
- USPS Notice 123, Price List, effective October 4, 2026, checked October 12, 2026
- USPS Priority Mail and Flat Rate service page, checked October 12, 2026
Get Discounted USPS Flat Rate Box Rates#
Print USPS Flat Rate Box labels below retail through I'd Ship That. Free to start, pay per label.
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