Pro rata calculator
Calculate a fair proportional amount and see every step—from part-time salary and holiday to rent, subscriptions, bonuses and benefits.
Important: This is a mathematical estimate. Employment contracts, leave policies, tenancy agreements, billing rules, tax requirements and local law can define different day-count or rounding methods.
Calculate any amount proportionally
A pro rata calculation gives someone or something a proportional share of a full amount. This calculator handles the most common search intents in one place: part-time salary, annual leave, part-period rent or recurring charges, and bonuses or benefits adjusted for hours and eligible time.
Pro rata amount = full amount × eligible sharePro rata formulas
| Calculation | Formula | Best used for |
|---|---|---|
| Salary | Full salary × your hours ÷ full-time hours | Part-time annual, monthly and weekly gross pay |
| Annual leave | Full leave × your schedule ÷ full-time schedule | Holiday days or hours for part-time staff |
| Rent or cost | Full charge ÷ full units × used units | Partial-month rent, subscriptions and service fees |
| Bonus or benefit | Full amount × work fraction × time fraction | Bonuses, allowances and annual benefits |
How to calculate pro rata salary
Start with the gross annual salary for a comparable full-time role. Divide the part-time weekly hours by the full-time weekly hours to find the full-time-equivalent work fraction, then multiply the full-time salary by that fraction. If employment covers only part of the year, multiply the annual pro rata salary by eligible months divided by 12.
The employee works 60% of full-time hours, so the ongoing pro rata salary is £25,200 a year. For 8 eligible months, the estimated pay for that period is £16,800.
How to calculate pro rata annual leave
Use the same unit for the full-time entitlement and the result. If leave is recorded in days, compare days worked per week. If workdays have different lengths, calculating in hours can be more accurate. A full-time allowance of 28 days adjusted from five days per week to three days per week is 16.8 days for a full leave year. For nine eligible months, it is 12.6 days.
Public holidays, carry-over, minimum statutory leave, compressed hours and employer rounding rules may require additional adjustments.
How to calculate pro rata rent or a recurring charge
Divide the full-period amount by the number of units in that billing period, then multiply by the chargeable units. For example, £1,200 divided by 30 days gives a daily rate of £40. Ten chargeable days cost £400, leaving £800 of the original period amount unallocated.
Check the agreement before choosing a day-count method. Some contracts use actual calendar days, a fixed 30-day month, weekly rates or another convention.
Pro rata bonus and benefit example
For a £5,000 full-time annual bonus, an employee working 24 of 40 weekly hours has a 60% work fraction. If the employee is eligible for nine of twelve months, the time fraction is 75%. The result is £5,000 × 0.60 × 0.75 = £2,250.
Rounding a pro rata result
The calculator keeps unrounded values throughout the calculation and rounds only for display. Money is normally shown to two decimal places. Leave is shown with up to two decimals because employers may round to a half-day, quarter-hour or another increment. Apply the rule stated in the relevant policy, contract or agreement.
Frequently asked questions
What does pro rata mean?
Pro rata means allocating an amount in proportion to a share of time, work, usage or entitlement. A person working 60% of full-time hours would usually receive 60% of a comparable full-time amount, subject to the relevant contract or policy.
How do I calculate a pro rata salary?
Divide the employee’s weekly hours by the full-time weekly hours, then multiply that ratio by the full-time annual salary. If the person works only part of the year, multiply again by eligible months divided by 12.
How is pro rata annual leave calculated?
Multiply the full-time leave allowance by the part-time work schedule divided by the full-time schedule. For employment during only part of the leave year, multiply again by eligible months divided by 12.
Can I calculate pro rata rent for part of a month?
Yes. Enter the full rent amount, the number of days in the billing period and the number of chargeable days. The calculator divides the amount by total period days and multiplies by chargeable days.
Should pro rata amounts be rounded up or down?
The calculator keeps full precision internally and displays sensible decimal places. A contract, employer policy, tenancy agreement or local law may require a specific rounding rule, so apply that rule to the final result.
Does changing the currency convert the amount?
No. Currency selection changes the symbol and number formatting only. It does not perform an exchange-rate conversion.
Calculation note
This calculator provides a general proportional calculation and does not interpret an employment contract, leave policy, tenancy agreement, tax rule or local law. Confirm which base amount, day-count method, eligible period and rounding convention apply before relying on the result.