Working Days vs Calendar Days: Salary Proration
When payroll departments process mid-month starts or terminations, they choose between two core math formulas: working days (260-day year) or calendar days (365-day year). Both methods convert annual salary into a daily rate, but payouts vary slightly.
Here is how both accounting methods work in real payroll systems.
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Method 1: 260 Working Days (US Standard)
The 260 working days method assumes 5 working days per week across 52 weeks a year (52 x 5 = 260). Weekends are excluded from the daily rate denominator.
For an $85,000 annual salary:
- Daily rate: $85,000 / 260 = $326.92 per workday
- If you work 10 workdays in a partial month: 10 x $326.92 = $3,269.20
Method 2: 365 Calendar Days
The 365 calendar days method spreads your annual salary across every calendar day of the year, including weekends.
For the same $85,000 annual salary:
- Daily rate: $85,000 / 365 = $232.88 per calendar day
- If you are on payroll for 14 calendar days (including weekends): 14 x $232.88 = $3,260.32
Which Method Do Most Companies Use?
Over 85% of US corporate payroll software relies on the 260 working days standard. It aligns cleanly with 40-hour workweeks and overtime calculations under the Fair Labor Standards Act.
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