How many 1st class stamps to use on heavy letters?

In our office, we buy Royal Mail stamps in ready to use denominations of “1st Class”, “2nd Class”, “Large 1st Class” and “Large 2nd Class”. However, these are only useful for 100g weight letters.

For heavy letters, we can use multiples of these stamps. I noticed I was routinely having to do the calculation in my head as to what is the optimum combination of stamps. For example, what to stick on a 500g 2nd class large letter. I know that’s £1.58, I know the stamps represent the 100g values, so 1st=65p 2nd=56p Large_1st=98p and Large_2nd=76p.

It’s not too hard to work out, but it takes time and gets harder with bigger letters and parcels.

For a coding challenge, I wrote “Stampulator“. It’s a single web page that tells us which combinations of stamps to use, so for the 500g 2nd Class large letter, £1.58 example, we need 1 x 1st class and 1x Large 1st class. That’s over by 5p, but it’s the nearest value to the cost.

I also made it so that if I have different value stamps or a different target value to reach (say; special offer or I’ve been slow to update the values when Royal Mail prices change) I can input those and get an instant result.

I then printed the page and stuck it buy our post box.  Stampulator is on my web server and free to use – it works well from a mobile phone too.

Post a comment here if it’s useful and that’ll encourage me to keep it up to date.

24 thoughts on “How many 1st class stamps to use on heavy letters?”

  1. Hello,

    I have a question.
    Can I use for exapmle 2x RED LARGE STAMPS for a large letter ( 1st class) up to 500g instead 2x red class and 1x blue class If I will buy cheaper Large stamps let’s say from an ebay?

    Thank you for a stampulator si very helpful.

    1. You can use any combination of stamps that match (or exceed) the required postage value.

      For some values, you can match the required postage with different combinations but stampulator only picks the one match. If there’s interest, I could make it so you can follow a link by the result to see other exact combinations of stamps that match the target value.

      Example: If you have stamp values of 10p and 20p, your target is 40p, you could reach that by having
      [4 x 20p], [2 x 10p + 1 x 20p] or [2 x 20p]. Stampulator will only display one.

  2. Hi, I am very glad that I bumped into your article Steve because I didn’t even realise that we could use traditional stamps on Large Letter and Small Parcels! The ‘Stampulator’ is an excellent coding program and I managed to use it successfully earlier today before I went to the Post Office. I have now bookmarked your website for future use. Thank you.
    Please keep up the great work 🙂

  3. Hi again, your ‘Stampulator’ is fantastic and very helpful. Is there any chance you are working on an update for latest stamp (2019) changes?

  4. I want to send a large letter 2nd class. I have 2x2nd standard size [2nd not 61p] and a 10p. Is that OK?
    Thanks

      1. Yes, as long as the combination of stamps add up to or exceed the required postage you’re good to go. A “2nd Class” stamp is currently equal to 61p and counted as such, so 2 of those plus a 10p stamp meets the value.

        This also means you can buy a stamp marked “second class” (as opposed to a stamp with a numeric value on it) today for 61p and when the prices go up it will still count as a second class stamp at the new higher value.

  5. Prices have gone up again – are you able to update? Super useful, especially in lockdown. Thanks!

  6. I’ve been waiting for this! And using my own totally unteccie not to mention unsatisfactory excel trial and error version. So helpful thank you. Also still using stamps I bought in bulk 9 years ago. Must have saved a penny or two!

  7. Hi Steve, Great calculator but it lacks what I need it for.

    For me I need more stamp options.

    Great for 1st / 2nd class standard and Large sizes.
    Doesn’t work as there is wastage!

    Wouldn’t it be better to under cost the costing rather than over cost?.

    With the under costing I could then add all the extra stamps that I needed.
    Over costing it as you currently have it would mean I will always be a couple of pence in loss.

    Would it be possible that you could add more stamp combinations options?

    As an example my partner is sending a Large letter 2nd class letter to her father with the weight of it being approximately 470 grms.

    I wanted to work out how many stamps that I needed.

    The cost to send is £1.99 because of the weight being 470 grms.

    As I got loads and loads of stamps. Mostly:
    1st Class Standard @ 100grms – £0.85
    1st Class Large @ 100grms – £1.29
    2nd Class Standard @ 100grms – £0.66
    2nd Class Large @ 100grms – £0.96

    Large 2nd Class Letter
    weighing 500grms
    Price: £1.99

    I worked it out with one 1st Class Large stamp costing £1.29
    One 2nd Class standard stamp costing £0.66.
    and then I added two 2pence stamps
    Total: £1.99

    Or

    Two 2nd Class Large stampS costing £0.96 = £1.92
    One 5-pence
    One 2-pence
    Total: £1.99

    And so on –

    I hope you understand my examples

    Looking for a calculator that can calculate the highest value downwards without waste.

    Can you do this?

    1. > Wouldn’t it be better to under cost the costing rather than over cost?.
      No!
      If your stamp value is less than required, the Royal Mail won’t deliver and will charge the under payment to the receiver along with a handling charge.

      >With the under costing I could then add all the extra stamps that I needed.
      >Over costing it as you currently have it would mean I will always be a couple of pence in loss.
      This is true, we could buy stamps of 1p/5p/10p etc and put the exact postage value on. However;
      * we don’t send very much post,
      * we get the benefit of the ‘1st class’ stamp even once the price has been increased (we buy perhaps £100 of stamps every couple of months)
      * most of the post we do send fits within a multiple of the 1st/2nd/L1st/L2nd stamps
      * If you’re sending lots of packages outside of the standard stamp range, check the royal mail online pricing options. You can buy an exact value stamp/label to print at home. We occasionally use that for tracked post (signed for/special delivery)

      >Would it be possible that you could add more stamp combinations options?
      > Looking for a calculator that can calculate the highest value downwards without waste.

      I think you’ve got enough on the page already. It takes 4 stamp values and you can change them to suit the values you have. You can also set a ‘target’ value in case you need to add signed for, calculate an international postage cost, etc .
      So, change one of the stamps to say, 1p, and you’ll probably get an exact match using up to 36 stamps.

      > As an example my partner is sending a Large letter 2nd class letter to her father with the weight of it > being approximately 470 grms.
      >I wanted to work out how many stamps that I needed.
      >
      >I worked it out with one 1st Class Large stamp costing £1.29
      >One 2nd Class standard stamp costing £0.66.
      >and then I added two 2pence stamps
      >Total: £1.99

      So to use your 2p stamps, replace one of the 4 preset values. EG: I just replaced Stamp4, the “96p Large 2nd” with 2p and it calculated the same combination as you did. There’s often more than one way get an exact match too, quick mental arithmetic suggests 35 x 2p stamps + 1 x large 1st.

      I hope that helps,
      Steve

  8. I love this, made my job a whole lot easier , I just jump on this website and don’t even need to think doing the maths. Thanks Steve please keep up the good work.

  9. I use this tool all the time for work, it’s really handy as it lives on my bookmark bar.

    Any chance you could update for the new stamp prices please?

    Ta

  10. I used Stampulator for the first time today: it’s great!
    Any chance of updating it for the new prices (they went up on 4th April).

  11. Hi Steve. This is (almost) perfect for me. I inherited a large number of smaller denomination stamps that I’m hoping to use for an ebay clearout, would you be able to update the page to more than 4 stamp prices or is that too big a challenge coding wise?

    1. You can put four of your own values in. So if you have 1p, 2p,5p and 10p the calculator will use the max of 36 stamps for just the standard letter sizes/weights.
      If you only have 3 stamp values, replace the last one with a high number like 999 and it won’t get used in the calculations.

      I could extend to 5 stamp values (or more!) if you can convince me more than 4 denominations is useful 🙂

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