Prorate calculator

Start with the amount for the complete period

New to the term? See what prorated means through rent, pay, fee and refund examples.

Enter the amount assigned to the full period, its start and end dates, and the service dates you want to allocate. The service range must sit entirely inside the full range. The calculator rejects dates outside it so an accidental overlap does not silently change the calculation.

For a monthly rental move, the prorated rent calculator supplies rent-specific methods and a month calendar. This general tool uses actual dates and a full-period amount instead. It does not assume that the period begins on the first of a month.

The formula

Daily amount = full-period amount ÷ counted full-period days
Prorated amount = daily amount × counted service days

Only the final allocated amount is rounded to cents. The daily amount retains its precision for the calculation. The unused portion is the original amount minus the rounded allocation; it is a mathematical remainder, not an automatic right to a refund.

Worked example: a January subscription

Suppose an illustrative subscription costs $310 for January 1–31, 2026. With both ends included, the full period has 31 days. Service from January 16–31 has 16 days. The daily amount is $10 and the allocation is $160; the unused portion is $150.

You can describe those same counted days using excluded end dates: full period January 1–February 1, service January 16–February 1. The result is still $160. Simply changing the convention without changing the end dates describes a different period.

A period that crosses month-end

Assume $600 covers April 10–May 9, 2026, with both ends included. There are 30 full-period days. Service from April 20–May 9 contains 20 days, giving $600 ÷ 30 × 20 = $400. The calculation follows those exact dates rather than using either calendar month as the denominator.

A full leap year has its actual counted days. For example, a $366 amount covering January 1–December 31, 2024 allocates $3 to February 28–March 1 when both ends count. Date differences are calculated without local time-of-day or daylight-saving adjustments.

Check that calendar days fit the task

Salary, insurance, utilities and cancellation credits can follow rules different from this simple allocation. A workday-based payroll calculation, a minimum billing period or an agreement that makes a charge non-proratable requires a different treatment. This tool does not read those terms or determine what is payable.

For advertised lease concessions, use the net effective rent calculator. A late fee uses its own chosen day-count and fee terms. Landlords comparing property scenarios can use rent versus sell.

Questions, answered