Fair shares, worked out properly
Pro rata is Latin for "in proportion". It is the rule behind a part-time salary, a first month's rent when you move in on the 19th, or a subscription that is cancelled halfway through a billing cycle. The idea is simple: pay for the share you used, at the same rate as the whole.
This pro rata calculator has two modes. Pro rata salary scales a full-time salary to the hours you actually work. Share of an amount takes any fee or charge and works out the part that belongs to a shorter period, in days, weeks or any other unit.
How to use it
- Choose Pro rata salary or Share of an amount.
- For a salary, enter the full-time yearly salary, the full-time hours a week, and your own hours.
- For any other amount, enter the full amount, the length of the full period, and the part used. Use the same unit for both.
- Read the pro rata figure, plus the share of the whole and the rate per unit.
The pro rata formula
pro rata amount = full amount × part used ÷ full period
pro rata salary = full-time salary × your hours ÷ full-time hoursBoth lines are the same idea. Find the rate for one unit, then multiply by the units used. A 1,200 monthly fee over 30 days is 40 a day, so 12 days cost 480.
Worked example: 24 hours a week on a 52,000 salary
A job pays $52,000 a year full time, for 40 hours a week. You will work 24 hours a week.
- Share of full time: 24 ÷ 40 = 0.6, which is 60%
- Pro rata salary: $52,000 × 0.6 = $31,200.00
- Each month: $31,200 ÷ 12 = $2,600.00
Your pro rata salary is $31,200.00 a year, or $2,600.00 a month before tax. The hourly rate is the same as full time, $25.00, which is what makes it fair.
Part of a month, by start date
Moving into a flat or starting a subscription partway through a month is where pro rata shows up most. Count the days you will use, including the first day, and divide by the days in that month.
| Days used | Share | Amount |
|---|---|---|
| 5 | 16.67% | 200 |
| 10 | 33.33% | 400 |
| 12 | 40% | 480 |
| 15 | 50% | 600 |
| 20 | 66.67% | 800 |
Some landlords and companies divide by 30 for every month, or by 365 days and then multiply by 12, which gives slightly different answers. Check which they use; the date calculator counts the days for you.
Where pro rata goes wrong
- Mixing units. If the full period is in days, the part used must be in days too.
- Forgetting holiday entitlement. A part-time job usually comes with a pro rata share of paid leave as well as pay.
- Leaving out the first or last day. Agree which days count before you send a bill.
- Treating pro rata pay as take-home pay. Tax and other deductions still apply. The hourly to salary calculator helps compare hourly offers.
Frequently asked questions
How do I calculate a pro rata salary?
Divide your hours by the full-time hours, then multiply the full-time salary by the result. For 30 hours a week against a 37.5 hour full-time week on 45,000, that is 30 ÷ 37.5 = 0.8, and 45,000 × 0.8 = 36,000. Enter the three numbers above and the calculator shows the monthly figure as well.
What does pro rata mean?
It means in proportion. A pro rata amount is a share of a total that matches the share of time, hours or use. Working three days out of five gets three fifths of the full-time pay; using 12 days of a 30 day month costs 12 thirtieths of the monthly fee.
How do I pro rata rent for part of a month?
Divide the monthly rent by the number of days in that month to get a daily rate, then multiply by the days you will live there. For 1,500 rent in a 31 day month, moving in on the 20th means 12 days, so 1,500 ÷ 31 × 12 = 580.65. Choose Share of an amount to do this.
Is holiday pro rata as well?
Usually, yes. Part-time workers in many countries are entitled to the same paid leave as full-time staff, scaled to their hours. Someone working 60% of full time on a job with 25 days of leave would typically get 15 days. Check your contract and local employment rules.
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