Proration calculator
Compute an amount prorated by days or shares (rent, subscription).
- Instant
- Free
- Private (processed locally)
- No sign-up
Prorate an amount, simply
Whether you move in mid-month or cancel a subscription, the calculation is the same: amount × used portion ÷ total. The tool shows the amount due, the remainder and the proportion.
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Total amount
The rent or full price for the period.
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Total
The number of days (or shares) in the period.
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Used portion
The days actually due or consumed.
Example: rent for a partial month
| Item | Value |
|---|---|
| Total amount | $1000 / month |
| Total (days in month) | 30 |
| Used portion (days occupied) | 21 |
| Prorated amount | 1000 × 21/30 = $700 |
| Remainder | $300 |
| Proportion | 70% |
Instant calculation in your browser. Check the day convention (actual or 30-day basis) set by your contract.
Frequently asked questions
How does proration work?
Amount due = total amount × (used portion ÷ total). Example: a $1000 rent for 21 days occupied out of 30 = 1000 × 21/30 = $700. The remainder ($300) corresponds to the unoccupied days.
How do I prorate rent for a partial month?
Count the days actually occupied, from the move-in day to the end of the month inclusive. For a move-in on the 10th of a 30-day month: 30 − 10 + 1 = 21 days. Enter 30 as total and 21 as used portion.
Days or shares: what is the difference?
It is the same formula, only the label changes. “Days” suits pro rata temporis (rent, subscription); “shares” suits a split (dividing a bill by quotas, for instance).
How many days should I use for a month?
It depends on the contract: the actual number of days in the month (28 to 31) or a fixed 30-day basis. Check the applicable convention; the tool accepts any total.