Shipping · USPS
USPS large envelope postage by the ounce.
Type the weight of your 9 x 12 or other large envelope to get the retail First-Class Mail flat price, plus the full 1 to 13 oz table.
A 1 oz large envelope (flat) costs $1.69. Each additional ounce adds about $0.29 to $0.31: 8 oz is $3.72 and 13 oz is $5.24.
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USPS large envelope (flat) postage by ounce
| Weight | Postage |
|---|---|
| Up to 1 oz | $1.69 |
| Up to 2 oz | $1.98 |
| Up to 3 oz | $2.27 |
| Up to 4 oz | $2.56 |
| Up to 5 oz | $2.85 |
| Up to 6 oz | $3.14 |
| Up to 7 oz | $3.43 |
| Up to 8 oz | $3.72 |
| Up to 9 oz | $4.02 |
| Up to 10 oz | $4.32 |
| Up to 11 oz | $4.62 |
| Up to 12 oz | $4.93 |
| Up to 13 oz | $5.24 |
What counts as a large envelope?
Under DMM 101.2.1, flat-size mail is more than 11-1/2 inches long, or more than 6-1/8 inches high, or more than 1/4 inch thick, and no more than 15 inches long, 12 inches high and 3/4 inch thick. It must be flexible, rectangular and uniformly thick. A flat-size piece that is rigid, nonrectangular or not uniformly thick is a parcel (DMM 101.6.4 and Notice 123 note 2), so a stiff or lumpy envelope should be priced on the Ground Advantage page.
A letter-size piece that weighs more than 3.5 oz is also charged these flat prices (DMM 101.1.1), and First-Class Mail letters and flats may not exceed 13 oz (DMM 101.6.1).
Frequently asked questions
How much is postage for a large envelope?
A large envelope up to 1 oz is $1.69 and 13 oz is $5.24 at retail (Notice 123 effective October 4, 2026). Prices rise at every ounce in between.
How much is postage for a 9 x 12 envelope?
A 9 x 12 envelope is a large envelope (flat). Weigh it: 2 oz is $1.98, 4 oz is $2.56, 8 oz is $3.72, 13 oz is $5.24. Heavier or rigid pieces are priced as parcels.
What if my envelope is over 13 oz?
The retail large envelope table stops at 13 oz. Use USPS Ground Advantage (from 4 oz up to 70 lb) or Priority Mail, both priced by weight and zone on this site.
What is the maximum size of a large envelope?
DMM 101.2.1 allows up to 15 inches long, 12 inches high and 3/4 inch thick. It must be flexible, rectangular and uniformly thick; otherwise it is priced as a parcel.
When do USPS prices change?
USPS usually updates its prices in January and July and can also change them at other times. This page is built from Notice 123 effective October 4, 2026. Check the effective date at the top of the official Notice 123; if a newer one is in force, use its figures.
Sources
Checked
- USPS Notice 123, Price List (HTML), effective October 4, 2026
- USPS Notice 123, Price List (PDF)
- DMM 101.2 and 101.6: retail physical standards for flats and First-Class Mail weight limit
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Prices change: check the date
These figures are USPS list prices from Notice 123 (Price List), effective October 4, 2026, read on 18 October 2026. USPS usually updates prices in January and July and can change them at other times, so if today is after a newer Notice 123 took effect, the official notice wins. Extra services (insurance, tracking add-ons, signature, pickup) and taxes are not included.