Trading card postage calculator.

What this calculator does

The question behind this tool is the one sellers keep asking: how many cards can go in one stamp. The honest answer depends on weight, thickness and whether the piece is rigid, and USPS publishes all three rules. A letter-size piece can weigh up to 3.5 oz and be at most 1/4 inch thick; above that it pays large-envelope prices. A piece that is rigid, or whose length divided by height falls outside 1.3 to 2.5, is nonmachinable and pays a $0.49 surcharge on top of the letter price.

Enter what you actually weigh and measure. The page prices the packed envelope as a letter when it qualifies, shows the large-envelope price next to it, and lists the most cards that fit under each letter price step so you can see where the next stamp starts. It covers United States domestic First-Class Mail letters and large envelopes only; parcels, tracking and insurance are out of scope.

Worked example

Four loose cards at 1.8 g each plus a 10 g packed envelope weigh 17.2 g, which is 0.61 oz. In a 6.5 by 3.5 inch envelope the length-to-height ratio is 1.86, inside the 1.3 to 2.5 limit, and the stack is 0.04 in thick. That is a 1 oz letter at $0.82.

Put the same four cards in a rigid holder and the piece becomes nonmachinable: $0.82 plus the $0.49 surcharge is $1.31. At 20 cards the weight is 1.62 oz and the letter price steps up to $1.11. Prices are from the USPS Notice 123 list headed "Effective October 04, 2026".

How it is calculated

Weight = cards x (grams per card + holder grams) + packaging grams, converted to ounces at 28.349523125 g per oz. Thickness is built the same way in inches. A piece is treated as letter-size if it is 5 to 11.5 in long, 3.5 to 6.125 in high, 0.007 to 0.25 in thick and no more than 3.5 oz (USPS DMM 101, section 1.1). Letter prices by weight not over: 1 oz $0.82, 2 oz $1.11, 3 oz $1.40, 3.5 oz $1.69. Large envelope prices run from $1.69 at 1 oz to $5.24 at 13 oz. The $0.49 nonmachinable surcharge is added when the piece is rigid or its length divided by height is under 1.3 or over 2.5 (DMM 101, section 1.2). Last checked 2026-10-26.

What this does not cover

• Domestic United States First-Class Mail letters and large envelopes only. Canada Post, Royal Mail and international rates are not included.
• Over 13 oz is a parcel, which is not priced here.
• Metered, commercial and Ground Advantage prices are different from the stamped retail prices shown.
• Large-envelope pieces have their own flexibility rules that this planner does not check.
• USPS changes its prices; confirm against the current Notice 123 before printing postage.