This page calculates how many 1st/2nd class stamps you need for large letters and parcels.
Read my blog about why I created this here. When Royal Mail prices change please prompt me via a comment on my blog or messge me via Mastodon(https://mastodon.me.uk/@Sroot) and I'll update the calculations. thanks!
I was asked for a version that shows the stamps used to be below the target value. You can find that at https://stampulator.sroot.eu/underpaid.html
If you're sending parcels, you might want to check Royal Mail online (also known as Click and Drop) pricing. They sometimes have discounts or offer free collections. https://www.royalmail.com/current-postage-prices currently links to both price lists. Example from 2025, online price for a 10KG parcel is currently £7.65 and the stamp/over the counter price is £8.99
I designed this page to be printable. It makes for a very long poster, useful for quick reference.
By default, it's assumed you have the standard UK 1st (£1.80p), 2nd (91p), Large 1st (£3.30p) and Large 2nd (£1.55p) which are are the Post Office price guide April 2026 prices from Royal Mail (link also includes size and weight limits). Alternatively, enter the values of the stamps you have here and press submit. If you don't need all 4 values use a high number like 9999 so it won't be suggested in the calculation. If you'd like a page for a different country or values comment on my blog and I'll see what I can do.
Known limitations: Can only use up to 9 of each type of stamp (thus 36 stamps in total)
| Your target values | 180 |
| Size | Weight (up to) | First Class | Second Class | ||
|---|---|---|---|---|---|
| Letter | 100g | 180 | 91 | ||
| Large Letter | 100g | 330 | 155 | ||
| 250g | 360 | 190 | |||
| 500g | 360 | 240 | |||
| 750g | 360 | 270 | |||
| Small Parcel | 2kg | 545 | 425 | ||
| Medium Parcel | 2kg | 805 | 695 | ||
| 10kg | 1005 | 875 | |||
| 20kg | 1545 | 1315 | |||
| Size | Weight (up to) | First Class | Second Class | ||
|---|---|---|---|---|---|
| Letter | 100g | 380 | 291 | ||
| Large Letter | 100g | 530 | 355 | ||
| 250g | 560 | 390 | |||
| 500g | 560 | 440 | |||
| 750g | 560 | 470 | |||
| Small Parcel | 2kg | 705 | 585 | ||
| Medium Parcel | 2kg | 965 | 855 | ||
| 10kg | 1165 | 1035 | |||
| 20kg | 1705 | 1475 | |||