Recently, I’ve had a couple of requests from users of the site to have a pro-rata calculator on the site, so you can work out what your new pay would be if you go down to reduced hours or enter a job share of some sort. Unfortunately, I’ve not had time to make this new tool, but it is easy to use the existing calculator to work out your pro-rata pay.

For example, if you are working 20 hours a week instead of 37.5:

  1. If you know the hourly rate for the job, use the Hourly Rate Calculator, enter that rate and 20 hours – the calculator will show you the take home pay.
  2. If you just know the annual salary for 37.5 hours a week, first divide the salary by 37.5, then multiply it by 20. Enter this new salary into the normal calculator and it should give you the right information.

According to HMRC, tax, NI etc are all worked out the same whether you worked 37.5 hours to earn the money, or just 20 (or 1!). The above tricks can show you what you need to know until I have time to create a pro-rata calculator.

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19 Comments to Pro-rata calculations

  1. Sorry, are you sure your calculations are right?! Your weekly figures seem right but not your monthly ones.

    I work a temporary job for £10.50 per hour for 30 hours a week with no sick pay and holiday pay pro rata. I got a monthly pay slip this week based on 4 weeks, and my gross pay was £1181.25 because I had to drop one day, so for that week I was paid £236.25. They deducted £314.06, £77.66 for NI and £236.40. I walked away with a minty £867.19 which I’m not at all happy with. Was that 20% BR tax?

    But for four weeks at £315 per week, which is correct, I should get £1260 gross – not £1365 as you suggest, surely? So have they overcharged my NI? I’ve queried it with them, quoting the figures I got from your site, but now I’m wondering because your monthly figures seem way off. What else are you taking into consideration there?

  2. Tracey Mitchell on October 3rd, 2009
  3. Hi Tracey,

    I think there are two things going on here, firstly a comparison of weekly and monthly, and secondly the tax your employer has taken off you.

    First thing is to note is that a month is not exactly 4 weeks. 4 weeks would be 28 days, not 30 or 31 – so the monthly value is more than 4 times the weekly value. In fact, the calculator divides the annual figures by 12 to give the monthly figures, and by 52 for the weekly figures. So that’s why 4 times £315 is not £1,365

    Secondly, it seems to me that you have been charged too much tax. If you are new to the job, they may have used “emergency tax”, where they don’t know your tax code. Without your tax code, they can’t give you your personal tax-free allowance, so they have taxed all of your income. I’m sure they will clarify this with you – most employers will correct this for your next payslip, and may even refund you the overcharged amount (so next month might be more than you expect!).

    I hope this helps, and as always your employer should be able to explain your payslip to you!

  4. admin on October 3rd, 2009
  5. Thank you for the explanation.

    I did challenge them about the tax and they then told me I had to complete a P46, in order for them to obtain a correct tax code for me and get me off BR.

    I had given them a P45 from my previous temp role which had had a BR tax code with it (because I had one and because I thought P45s were preferable over P46s!) but I hadn’t noticed the deduction as much because that role was weekly paid. For the last seven years I have also worked on and off for a nurse ‘bank’ for which I have a proper tax code – I don’t see why I can’t pass that on to this current employer, but apparently each new job needs a new tax code!

    (I’ve only been working nineteen years, like!)

    I know for a fact my name is mud with the inland revenue with all my temp roles because they as much as said they’re fed up with giving me rebates!

  6. Tracey Mitchell on October 14th, 2009
  7. Hi, I have a question about tax free allowance. I started my new job in Nov 2010, and thus will only be working 5 months this tax year (1 Nov – 31 Mar). I understand that the current tax free allowance is at £6475. Will I be getting the full £6475 tax free allowance, or will there be some sort of a pro rata calculation (i.e. £6475 x 5/12 = £2698)?

  8. Jin on February 3rd, 2011
  9. Hi Jin,

    If you didn’t have any income between April 2010 and starting your new job in November, you should be entitled to your full allowance of £6,475 for the 2010-11 tax year (although the allowance can be affected by other benefits – see the post on tax codes). Most employers will automatically work out the correct amount for you to take home this tax year, and spread that over your payslips. You may find in April that you take home less than you do now, since your tax-free allowance will be spread over the whole year rather than just 5 months! If you are uncertain, check with your employer’s finance or HR department – they will be able to explain things to you. If you have paid too much tax this year you can normally claim it back from your local tax office.

  10. admin on February 5th, 2011
  11. hi, while you are developing a tool for reduced hours working, please could you consider developing something for reduced weeks working. I am a term time only worker, working 37 weeks per year and would like help to calculate earnings please. thanks

  12. bobby on March 14th, 2011
  13. […] Calculator – I have finally created it and added it to the site. As I have mentioned in an earlier post, pro-rata salary is normally calculated quite easily. For reduced hours, most employers will […]

  14. Pro-rata Salary Calculator added | The Salary Calculator on April 2nd, 2012
  15. Hi Bobby,

    Sorry I missed your comment last year! I have just created a new pro-rata calculator here:

    It asks you to enter full-time hours and pro-rata hours, but you can also enter weeks (the calculation is the same). So, in your example, you could enter 52 into the full-time hours box and 37 in the pro-rata hours box, and it will calculate the salary pro-rata for you.

    I hope this helps!

  16. admin on April 2nd, 2012
  17. If the full-time working hours are 35hrs per week but a person gets a pro-rata bonus of £400 but works 41 contracted hrs per week for the same company, should the bonus go up as it goes down for anyone working less than 35hrs?

  18. Duncan Martin on March 28th, 2013
  19. Hi Duncan,

    It would depend on how the employer works out the bonuses for each of their staff. In my experience, a bonus is often a percentage of the staff member’s normal salary – so if they were getting paid more because they worked 41 hours per week rather than 35, the bonus would be proportionately larger. However, it is possible that the employer might have a cap on the bonus or try to treat additional hours as overtime rather than contracted (and therefore not included in bonus calculations). The HR or payroll department should be able to explain how the bonuses are worked out.

  20. admin on March 28th, 2013
  21. hi
    I receive 700 euro pension a month from Ireland but when I receive it in pounds it is £541.86 I have checked the exchange rate and I am £50. pounds short can you explain please thank you.

  22. john coogan on May 20th, 2013
  23. Hi John,

    I’m afraid I don’t know what would cause that. It is possible that there is a commission fee for changing the currency charged by your pension provider, their bank, or your bank – or maybe some tax is being deducted before it is transferred. I would suggest a first port of call be your pension provider, they might be able to explain why this is happening.

  24. admin on May 20th, 2013
  25. Hello, I am due to start a new job next week. The shift pattern is 4 on 4 off, 12.5 hours per shift at £8 an hour. It’s with an agency so I’ll be paid weekly. I’m trying to work out how much I’ll take home weekly, monthly and annually and how much tax and NI I’ll pay. Due to the shift pattern and it being weekly pay I don’t know how to. Can you help?

  26. Sarah on July 21st, 2015
  27. Hi Sarah,
    I don’t have any experience with this specific situation, but this is how I imagine it will work out. Some weeks you will work 3 shifts and have 4 days off, others you’ll work 4 and have 3 off (which particular days you work will change from week to week, but it’s always either 3 days or 4 days). 3 shifts at 12.5 hours is 37.5 hours in the week, 4 shifts brings it up to 50 hours. Assuming that you get paid each week according to how many shifts you did:
    Go to the hourly wage calculator and enter £8 as the hourly wage, and 37.5 hours. This will give you the amount you’ll earn in a 3-shift week. Now change 37.5 to 50, and that’ll show you what you’ll get in a 4-shift week.
    It’s possible that the agency will pay you same each week, an average of the two amounts – to see this, enter 43.75 (the average number of hours you’ll work) in the hourly wage calculator. This will also give you your effective annual salary (in the Yearly Gross Income column).
    Now, I’m not certain about any of this, and I should point out that it’s likely that your take-home pay may be a little different from this each week – by a few pounds here or there – because tax is worked out cumulatively. Brief version: your tax in a 3-shift week will take into account the fact that the previous week was a 4-shift week, for example. Hopefully, though, this is of some use!

  28. admin on July 21st, 2015
  29. My daughter a staff nurse generally earns £1,700.00 per month she is currently on maternity leave and rather than have 8 weeks full pay them 18 weeks 1/2 pay plus SMP then 13 weeks SMP she asked for her wage to be averaged out she was on annual leave until the 27th june but this months wage is only £700.00 way below her direct debits is this correct please

  30. Sonia gregory on July 26th, 2015
  31. Hi Sonia,
    I’m afraid I don’t have any experience with Statutory Maternity Pay, so I don’t know how it is calculated and how your daughter’s employer might have worked it out. It is possible that her employer has averaged her salary over 52 weeks rather than the 39 that you have listed, that would obviously make the monthly amount lower. I would suggest that in the first instance ask her HR or Payroll department to talk you through the calculations for this month’s payslip – they should be able to tell you how they worked out the amount to pay her. If they can’t help, Citizens Advice will probably be able to offer some assistance too. Sorry I can’t help further!

  32. admin on July 26th, 2015
  33. Hello, I recently asked my employer how my pro rata wage is calculated as I honestly felt I was on a lower wage than my full time work colleagues. I work 22.5 hours per week, The full time wage is £17610 per annum. They sent me the following calculation:

    £17610 x 22.75 ÷ 38.75 = £10338 per annum pro rata (This is indeed the wage they pay me.)

    But your calculator says my wage should be £10612.65? Also I don’t understand the 22.75 either as it is really 22.5 ? Please help. Thanks

  34. Anne on October 23rd, 2015
  35. Hi Anne,
    When I try the numbers £17,610, 22.75 hours per week from 38.75 full-time hours in the calculator, I get £10,338 too – so the calculator matches your employer’s calculations. I’ve tried a few other numbers but I can’t get them to produce the result you got. It’s possible that you left the full-time hours as 37.5, which is what a lot of UK employers consider to be full time – this would make it look like you should get paid more than you do, since your hours would be a slightly larger fraction of that smaller full time amount.

    I’m afraid I don’t know why your employer thinks you work a quarter of an hour each week more than you think you do – I would suggest you check your contract for how long you should be working. Of course, if you are right, your employer might start paying you less (or asking you to work more)!

  36. admin on October 23rd, 2015
  37. Hello

    Thanks so much for your response ! You were indeed correct and I had entered the incorrect full time hours. So my employers calculations are right after all. I can now put this matter out of my mind. Thanks again.

  38. Anne on October 25th, 2015

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