Flat rate box prices and when a box beats the scale
Flat rate box prices for every USPS envelope and box, and the test that matters: for your weight and ZIP Codes, is the box cheaper than paying by weight?
Independent site, not the Postal Service: prices read in its own price files.
Example: 2 lb from 10001 to 90012· change a figure to see yours
Priority Mail Medium Flat Rate Box at the Post Office today
$25.80
Paying by weight is cheaper here ($22.55): the flat rate costs $3.25 more.
| Same box from Jan 17, 2027 (proposed) | $26.97 |
| Same, online label today | $22.02 |
| Priority Mail by weight, 2 lb, zone 8 | $22.55 |
Compiled by Radif Partners · How the prices are built
A Priority Mail flat rate box costs the same whatever it weighs, up to 70 pounds, and wherever it goes in the United States, as the Domestic Mail Manual states. Only boxes and envelopes made by the Postal Service and marked Flat Rate qualify. At a Post Office counter today the Flat Rate Envelope costs $13.90, the Small Flat Rate Box $14.65, the Medium $25.80 and the Large $36.10. These prices include the holiday increase in force until January 16, 2027. From January 17 the proposed base price of the Medium box is $24.30, or $26.97 once the 11% fuel surcharge is added, against $24.80 in July 2026. A box only saves money when the same package would cost more by weight: for a light package near home, paying by weight is cheaper; for a heavy one going far, the box wins.
Flat rate box prices: July 2026, today, online and 2027
The table follows each box through the three price lists of the Postal Service. Today's counter prices include the time-limited holiday change of October 4, 2026; the 2027 column is the proposed base price with the fuel surcharge.
| Envelope or box | July 2026 | Today | Today online | from Jan 17, 2027 |
|---|---|---|---|---|
| Flat Rate Envelope | $12.90 | $13.90 | $11.97 | $14.04 |
| Legal Flat Rate Envelope | $13.25 | $14.25 | $12.51 | $14.37 |
| Padded Flat Rate Envelope | $14.00 | $15.00 | $12.84 | $15.21 |
| Small Flat Rate Box | $13.65 | $14.65 | $12.95 | $14.87 |
| Medium Flat Rate Box | $24.80 | $25.80 | $22.02 | $26.97 |
| Large Flat Rate Box | $34.00 | $36.10 | $32.75 | $37.02 |
| Express Flat Rate Envelope | $35.90 | $38.25 | $33.46 | $38.74 |
| Express Legal Flat Rate Envelope | $36.20 | $38.55 | $33.78 | $39.07 |
| Express Padded Flat Rate Envelope | $36.90 | $39.25 | $34.05 | $39.79 |
Where the box starts to pay
The table gives, for a few weights, the first zone in which the box costs less than Priority Mail by weight at the counter. A 1-pound item only belongs in a Small box if it travels far; a 10-pound item in a Medium box saves money from zone 5.
| Package weight | Small box wins from | Medium box wins from | Large box wins from |
|---|---|---|---|
| 1 lb | zone 6 and up | zone 9 and up | never |
| 3 lb | zone 4 and up | zone 8 and up | zone 9 and up |
| 5 lb | zone 1 and up | zone 6 and up | zone 8 and up |
| 10 lb | zone 1 and up | zone 5 and up | zone 6 and up |
Your package in a flat rate box
Example: 10 lb from 10001 to 90012· change a figure to see yours
Priority Mail Medium Flat Rate Box at the Post Office today
$25.80
Cheaper than paying by weight ($63.40): the flat rate saves $37.60.
| Same box from Jan 17, 2027 (proposed) | $26.97 |
| Same, online label today | $22.02 |
| Priority Mail by weight, 10 lb, zone 8 | $63.40 |
Choosing the right box size
Start from the item, not the price. The Small box suits a phone, a book or a few jars of spices; the Medium price covers two box models, sold at one price; the Large box is for bulky but dense loads such as tools or canned goods. Any of them can be filled to 70 pounds. Fill the gaps with padding, because the box must protect its contents through the network like any parcel, then compare the box price with the price by weight in the calculator before you pay.
Ground Advantage is not part of this test and can be cheaper than both, as the cheapest way page shows. For the per-pound prices, see Priority Mail rates.