proratacalc Pro rata calculators that show their work.

FINANCIAL CALCULATOR

Pro Rata Calculator

This free pro rata calculator works out a proportional amount for any partial period — and shows the exact formula with your own numbers. Choose the day-count basis your employer, landlord, or contract actually uses, so your figure matches theirs.

Calculate a pro rata amount Sample values shown — edit any field to calculate instantly.

Pick Salary to scale an annual figure to your hours or days; pick Amount over a period for a one-off proportional split (rent, a fee, a refund).

Start from a common case:
$

Day-count basis

— why your number might differ

Counts the real number of days in both the period and the part you used. Leap years count Feb 29 automatically.

Count both the first and last day?
Pro rata amount
$840.00 That’s 70% of the full amount.
Per-day value: $40.00 · Days used: 21 of 30
Calculation method See the exact formula with your numbers
Day-count basis
Actual / actual
Endpoints
Inclusive
Counted days
21 of 30
  1. Days in the full period (Actual / actual): 30
  2. Days used (Actual / actual): 21
  3. Proportion used: 21 ÷ 30 = 0.70
  4. Pro rata amount: $1,200.00 × 0.70 = $840.00

Figures are illustrative. Change the day-count basis above to see how each convention moves the result.

The #1 confusion

Is that figure my pay — or a full-time figure?

Three different numbers get called the same thing, and mixing them up is the most common reason a pro rata amount looks wrong:

Full-time equivalent (FTE) the figure for someone doing the role full-time. A part-time job ad often quotes this so you can compare roles — it is not what you'd receive.
Pro rata gross the FTE figure scaled to your actual hours or days. This is what this calculator works out.
Net take-home your pro rata gross after tax and deductions. This calculator does not estimate tax — your take-home will be lower than the pro rata gross. To estimate take-home, use a paycheck / take-home pay calculator; pro rata only gives the gross figure.

▲ Why does my mid-month start change things?

If you start partway through a pay period, only the remaining days are paid that period. Two pay schedules also split a salary differently: biweekly pays 26 times a year, semi-monthly pays 24 — the same salary, a different amount per paycheck. Pick the matching divisor above so the split lines up with your employer's.

How it's calculated

In proportion — nothing more

Pro rata simply means in proportion. Take the value of one unit (one day, one month, one share), then multiply by the number of units that apply to you:

pro rata amount = full amount × (units used ÷ total units)

The only thing that changes the answer is how you count the units — which is exactly what the day-count basis above lets you control.

Questions

Frequently asked

What does pro rata mean on a job posting?
It means the salary shown is the full-time figure; your actual pay is that figure scaled to the hours or days you work. Use Mode B above to see your scaled amount.
Does pro rata include tax?
No. Pro rata is a proportion of the gross figure. Your take-home is lower because tax and deductions come off afterwards.
Why doesn't my pro rata pay match my employer's?
Usually the day-count basis or the pay-period divisor differs. Try Actual/365 vs Actual/actual, or switch between biweekly (26) and semi-monthly (24), and compare the steps above.
Inclusive or exclusive days — which should I use?
For rent, PTO, and accrual days, count both endpoints (inclusive). For interest-style calculations, the last day usually isn't counted (exclusive).

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