Proration Calculator

About This Tool

A proration calculator for splitting monthly charges by the number of days used. Enter the monthly fee, start date, and end date to instantly see the prorated amount. Ideal for subscription cancellations, mid-month sign-ups, and partial-month rent calculations.

Formula

• Prorated Amount = Monthly Fee × Days Used ÷ Base Days
• Days Used: Both the start and end dates are counted (e.g., Apr 1–Apr 10 = 10 days)
• Base Days: Either the actual number of days in the month (28–31) or a fixed 30 days
• Fractions below ¥1 are rounded down

Choosing a Day Count Basis

• Actual Days: For lease agreements, utility bills, etc., where fair apportionment based on month length is preferred
• Fixed 30 Days: For SaaS subscriptions, telecom charges, etc., where a uniform calculation regardless of month length is standard

Note: If the start date is after the end date, the result will be ¥0. For cross-month calculations, the actual days of the start month are used as the base.