Use one basis for the whole fraction
Prorated salary = annual salary × eligible units ÷ total units. The eligible and total counts must both be months, both be calendar days, both be working days, or both use the same custom unit.
Mixing units makes the fraction meaningless. The included amount plus the excluded amount should still reconcile to the entered annual gross salary before any separate payroll rounding.
Choose the basis that matches the decision
| Basis | Use it when | Check before entering |
|---|---|---|
| Months | The arrangement is defined in whole-month shares. | The model requires a 12-month total. |
| Calendar days | Eligibility is defined by dates on the calendar. | Confirm whether the relevant year has 365 or 366 days. |
| Working days | The agreement counts scheduled workdays. | Obtain the applicable working-day total rather than borrowing calendar days. |
| Custom units | A contract defines another consistent allocation unit. | Document what one unit means and use it for both counts. |
A nine-of-twelve-month example
For an annual salary of 84,000 with 9 eligible months out of 12, the calculator calculates a 75% eligible fraction. The included gross salary is 63,000 and the excluded portion is 21,000.
Months validate against a 12-month total. Calendar-day mode instead validates against 365 or 366; neither rule tells an employer which basis its contract must use.
Confirm the convention before relying on the result
- Find the salary period and proration basis in the contract, offer, or payroll documentation.
- Confirm the start and end boundaries and whether either endpoint is included.
- Ask how working days, leave, partial periods, and payroll cut-offs are handled.
- Expect payroll rounding to create small differences from the unrounded planning estimate.
Do not substitute a weekly-hours comparison
Prorated Salary allocates one annual amount across an eligible fraction of a period. Part-Time Salary Equivalent instead scales pay between weekly schedules while holding implied hourly pay constant. Open this calculator and its methodology when eligibility units—not weekly hours—drive the question.
How the Prorated Salary Calculator calculation works
proratedSalary = annualSalary × eligibleUnits ÷ totalUnits
- proratedSalary
- Prorated salary
- annualSalary
- Annual salary
- eligibleUnits
- Eligible units
- totalUnits
- Total units
The calculator and article use this relationship consistently; the article does not reimplement the calculation.
excludedSalary = annualSalary − proratedSalary
- excludedSalary
- Excluded salary portion
- annualSalary
- Annual salary
- eligibleUnits
- Eligible units
- totalUnits
- Total units
- basis
- Proration basis
The calculator and article use this relationship consistently; the article does not reimplement the calculation.
fraction = eligibleUnits ÷ totalUnits
- fraction
- Eligible fraction
- annualSalary
- Annual salary
- eligibleUnits
- Eligible units
- totalUnits
- Total units
- basis
- Proration basis
The calculator and article use this relationship consistently; the article does not reimplement the calculation.
An annual gross salary of 84,000 with 9 eligible months out of a 12-month year.
Inputs used in the Prorated Salary Calculator worked example
| Input | Entered value | What it represents | Source class |
|---|---|---|---|
| Annual salary | 84,000 currency units/year | Full annual gross salary before proration. | user record |
| Eligible units | 9 selected units | Months, days or custom units included. This is reduced visibly if it exceeds the basis total. | user record |
| Total units | 12 selected units | Months use 12; calendar days use 365 or 366. Other bases keep the entered total. | user record |
| Proration basis | Months | Choose months, calendar days, working days or another consistent unit. | user decision |
Choose the right Prorated Salary Calculator basis or mode
| Choice | How to use it |
|---|---|
| Months | Choose months, calendar days, working days or another consistent unit. |
| Calendar Days | Choose months, calendar days, working days or another consistent unit. |
| Working Days | Choose months, calendar days, working days or another consistent unit. |
| Custom | Choose months, calendar days, working days or another consistent unit. |
Worked example: Prorated Salary Calculator
The calculator normalizes the inputs above, applies Prorated salary, and returns the outputs below. The displayed result is therefore reproducible in the linked calculator.
| Measure | Result | Interpretation |
|---|---|---|
| Prorated salary | 63,000 currency units | Annual salary multiplied by the eligible fraction. |
| Excluded salary portion | 21,000 currency units | Annual salary minus the prorated amount. |
| Eligible fraction | 0.75 share of annual salary | Eligible units divided by total units. |
Interpret the result and test Eligible units
- Prorated salary: 63,000 currency units. Annual salary multiplied by the eligible fraction.
- Excluded salary portion: 21,000 currency units. Annual salary minus the prorated amount.
- Eligible fraction: 0.75 share of annual salary. Eligible units divided by total units.
| Result | Baseline | Changed-input scenario | How to read it |
|---|---|---|---|
| Prorated salary | 63,000 currency units | 70,000 currency units | Annual salary multiplied by the eligible fraction. |
| Excluded salary portion | 21,000 currency units | 14,000 currency units | Annual salary minus the prorated amount. |
| Eligible fraction | 0.75 share of annual salary | 0.83 share of annual salary | Eligible units divided by total units. |
Checks that are specific to Prorated Salary Calculator
- A full eligible period returns the full annual salary.
- Zero eligible units returns zero prorated salary.
- Eligible units above total units return an input error.
What this Prorated Salary Calculator guide includes and excludes
- Eligible and total units use the same consistent basis.
- Months basis uses exactly 12 total units; calendar days use 365 or 366.
- The annual salary is gross before tax.
Sources and method boundary
- Prorated Salary Calculator methodology — Wage101 (accessed 2026-07-27): Canonical formulas, units, validation, calculator behavior and limitations.