Prorate Calculator

To prorate means to allocate or divide a recurring periodic cost proportionately according to the exact duration of time used or occupied, rather than billing for the full standard cycle.

In property leasing, if a tenant takes occupancy midway through a month (for example, on the 18th of a 30-day month), prorated rent ensures they only pay for the 13 days they actually have access to the property. Proration is equally fundamental across utility billing, employee payroll, software user subscriptions, and insurance premiums.

To calculate prorated rent for a partial move-in or move-out month, follow this two-step formula:

Step 1: Daily Rental Rate = Monthly Rent ÷ Days in Target Month

Step 2: Prorated Rent Due = Daily Rental Rate × Billable Days of Occupancy

Note: The move-in day itself is almost universally included as a billable day because legal possession begins on that date (Billable Days = Total Days in Month - Move-In Date + 1).

Example: A tenant moves into an apartment on October 12th where monthly rent is $2,400. October has 31 days. The tenant occupies the unit for 31 - 12 + 1 = 20 billable days. The daily rate is $2,400 ÷ 31 = $77.419/day. Total prorated rent due is 20 × $77.419 = $1,548.39.

Under standard payroll and Department of Labor (FLSA) conventions for exempt salaried personnel, prorated compensation is calculated based on actual working days (business days) rather than total calendar days:

Daily Salary Rate = Annual Gross Salary ÷ Total Workdays in Year (typically 260 or 261 days)

Prorated Gross Pay = Daily Salary Rate × Actual Days Worked in Pay Period

Example: An employee hired at an $83,200 annual salary starts on a Wednesday and works 8 days during a standard 10-day biweekly pay period. Their daily rate is $83,200 ÷ 260 = $320.00/day. Their prorated gross pay for that initial pay cycle is 8 × $320.00 = $2,560.00.

The appropriate method depends on the contractual agreement and industry sector:

• 1. Actual Days in Month Method (Most Common & Recommended): Divides the monthly charge by the exact number of calendar days in that specific month (28/29 in February, 30 in April/June/September/November, 31 in others). It is standard across residential leasing (Zillow, TurboTenant) and legally reflects exact calendar duration.
• 2. Banker’s 30-Day Month Rule: Assumes every single month has exactly 30 days (Daily Rate = Monthly Rate ÷ 30). Widely utilized in commercial real estate, corporate bond accrued interest, and commercial equipment leases.
• 3. Annualized 365-Day Method: Multiplies the monthly rate by 12, then divides by 365 (Daily Rate = [Monthly Rate × 12] ÷ 365). Often mandated by corporate payroll systems and military allowances to maintain an identical daily rate throughout the entire year.

Always review the explicit language in your lease or employment agreement.

Yes, annual software subscriptions (SaaS), gym memberships, and insurance policies are routinely prorated for mid-term additions, tier upgrades, or cancellations.

Common implementations include:

• Mid-Cycle SaaS Seat Additions: When adding new employee licenses 120 days into a 365-day annual contract, providers charge only for the remaining 245 active days: Additional Cost = (Annual Seat Price ÷ 365) × 245 days.
• Insurance Cancellations (Pro-Rata Refund): If an insured party cancels an annual auto or home policy 100 days after inception, the insurer refunds the unearned premium for the remaining 265 days: Refund = Total Premium × (265 ÷ 365), unless a specific short-rate cancellation fee applies.