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How to prorate an amount in Excel and Google Sheets
Topic:Finance basicsExcel & Google Sheets
=A2/B2*C2✓
Verified example
Computed by a real spreadsheet engine on the sample data below.
| Full Amount | Total Days | Days Active | Prorated |
| 1200 | 30 | 15 | |
| 5000 | 31 | 20 | |
| 3600 | 28 | 7 | |
| 2400 | 30 | 30 |
=A2/B2*C2→600
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Step by step
- 1Column A = Full Amount, Column B = Total Days in Period, Column C = Days Active.
- 2In D2 enter =A2/B2*C2 to get the prorated amount.
- 3For a monthly prorate, B2 can reference DAY(EOMONTH(date,0)) to get the actual days in the month.
- 4Round if needed: =ROUND(A2/B2*C2,2).
Tips
- For mid-month starts, use EOMONTH and the start date to dynamically calculate the remaining days: =A2*(DAY(EOMONTH(StartDate,0))-DAY(StartDate)+1)/DAY(EOMONTH(StartDate,0)).
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Frequently asked
How do I prorate an annual amount to a partial year?
Divide by 365 (or 366 in a leap year) and multiply by days active: =AnnualAmount/365*DaysActive.
Should I use actual days or calendar days?
Most billing uses actual calendar days. For business-day prorating, use NETWORKDAYS to count working days instead.
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