Prorate Calculator
Calculate prorated amounts for rent, bills, subscriptions, salaries, and any periodic charge based on actual days used.
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Open CalculatorHow to Use This Calculator
Enter Full Amount
Type the full period charge, your monthly rent, annual subscription, or other recurring bill amount.
Select Billing Period
Choose whether the charge is monthly, annual, bi-weekly, weekly, or a custom number of days.
Enter Days Used
Type the number of days you actually used or occupied during the period. For move-ins, count from your start date to end of month.
Review Prorated Amount
See your exact prorated charge, daily rate, savings compared to the full amount, and percentage of the period used.
How We Calculate
Proration divides a fixed periodic charge by the total number of days in the billing period to derive a daily rate, then multiplies by the actual days used. This is the standard method used by landlords, employers, insurance companies, and subscription services across the United States.
For monthly billing, the calculator defaults to 30 days per month (the banker's month convention), which is the most common approach in lease agreements and commercial billing. Some landlords use the actual calendar days in the specific month (28, 29, 30, or 31), which you can override by entering a custom total. Annual proration uses 365 days by default. The formula is straightforward: Prorated Amount = (Full Amount ÷ Total Days) × Days Used.
This approach aligns with standard accounting practices documented by the American Institute of CPAs and commonly used in property management software like AppFolio and Buildium.
Sources & References
- American Institute of CPAs, Revenue Recognition & Proration Standards (aicpa.org)
- Nolo, Prorated Rent: How to Calculate and When It Applies (nolo.com)
- Investopedia, Proration Definition and Examples (investopedia.com)
Data last verified:
Frequently Asked Questions
Prorated rent is calculated by dividing the monthly rent by the number of days in the month, then multiplying by the number of days the tenant will occupy the unit. For example, if rent is $1,500/month for a 30-day month and the tenant moves in on the 15th, the prorated rent is ($1,500 ÷ 30) × 16 = $800. The move-in day itself is typically counted as an occupied day.
Both methods are legitimate. The 30-day (banker's month) method is simpler and used by many landlords and billing systems. The actual calendar day method (28-31 days) is more precise and may be specified in your lease or service agreement. Check your contract to see which method applies. If not specified, 30 days is the most common default.
Divide the full pay period salary by the total working days in that period, then multiply by the days actually worked. For salaried employees, use business days (typically 21-23 per month). For hourly or per-calendar-day calculations, use total calendar days. Many employers use the annual salary divided by 2,080 hours (52 weeks × 40 hours) for the most precise daily rate.
Typically yes, the move-in day counts as an occupied day. If you move in on March 15 in a 31-day month, you are charged for 17 days (March 15 through March 31). However, some lease agreements specify that the move-in day is not charged. Always check your specific lease terms for clarification on how move-in and move-out days are handled.
Divide the annual cost by 365 (or 366 for a leap year) to get the daily rate. Then multiply by the number of remaining days. For example, canceling a $120/year subscription with 200 days remaining: ($120 ÷ 365) × 200 = $65.75 refund or $54.25 prorated charge for the used portion.
In insurance, proration means adjusting a premium based on the actual coverage period. If you cancel a policy mid-term or make changes that affect your rate, the insurer calculates the prorated premium for the days covered. Some insurers use a "short rate" method that includes a penalty, while "pro rata" cancellation gives a true proportional refund.
If you use actual calendar days, yes, February proration will differ from March. A $1,500/month rent prorated for 10 days would be $535.71 in February (28 days) but $483.87 in March (31 days). Using the 30-day standard method avoids this variation, which is why many landlords prefer it for consistency.
For utilities, divide the total bill by the number of days in the billing cycle, then multiply by the days each party is responsible. If a roommate moves out mid-month on day 18 of a 30-day cycle with a $150 electric bill, their share is ($150 ÷ 30) × 18 = $90. The remaining tenant pays $60 for the final 12 days.
Most states do not have specific laws requiring prorated rent for partial months. However, it is standard practice in the rental industry and is typically addressed in the lease agreement. In some jurisdictions, tenants who give proper notice may be entitled to a prorated refund for unused days. California, for instance, requires landlords to refund prorated rent when a tenant provides adequate notice to vacate.
Proration divides a charge proportionally over time based on actual usage (like partial-month rent). Amortization spreads a debt or cost over a fixed schedule of payments with interest (like a mortgage). Proration is simpler, it is purely a time-based division. Amortization involves a payment schedule where each installment covers both principal and interest in changing proportions.
Prorate Calculator Team
Our editorial team includes financial researchers and property management professionals who verify every formula against AICPA standards, Nolo guidance, and the Uniform Residential Landlord and Tenant Act. We review and update all content quarterly.