Pro Rata Calculator
Calculate a proportional amount based on a total value and a partial period or quantity.
Published by:
isCalculator Editorial Team
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How to use this tool?
This calculator determines a pro rata (proportional) amount based on a total value over a full period, adjusted for a shorter partial period.
- Enter Total Value – The full amount (e.g., $1,200).
- Enter Total Period (days) – The full duration (e.g., 365 days).
- Enter Partial Period (days) – The shorter time you want to calculate for (e.g., 30 days). Must be 0 or more and cannot exceed the total period.
- Click "Calculate" – The result shows the pro rata amount and the formula used.
Formula: (Total Value ÷ Total Period) × Partial Period
Example: ($1,200 ÷ 365) × 30 = $98.63
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Frequently Asked Questions
Pro rata is a Latin term meaning 'in proportion'. It refers to the proportional allocation of a total amount based on a partial period or quantity.
The formula is: (Total Value / Total Period) × Partial Period. For example, if an annual salary of $50,000 is for 365 days, the pro rata for 30 days is (50000/365)*30 ≈ $4,109.59.
It is commonly used for salary adjustments (starting mid-month), rent for partial months, insurance premiums, dividends, and subscription fees.
