HesapHanem

Prorated Subscription Calculator

Charge fairly for partial periods

How it is calculated

You enter the full price of the billing period, the number of days in that period and the days already used. The tool works out the days left, then the daily rate, then the charge for what is left: remaining = total days − used days, daily = price ÷ total days, charge = daily × remaining. The result is the amount for the unused part of the period, which is what a customer pays when joining mid-cycle or the credit owed when cancelling. If used days exceed the period, remaining is set to 0 and the charge is $0.00. Money is shown in dollars rounded to cents; the daily rate is calculated unrounded before the charge. Different providers count the day of the change differently, so the result may differ by a day.

Worked example

A plan costs 45 for a 31-day billing period and 10 days have passed. Remaining days = 31 − 10 = 21. Daily rate = 45 ÷ 31 = 1.4516, shown as $1.45. Charge = 1.4516 × 21 = $30.48. Notice that multiplying the displayed $1.45 by 21 would give $30.45, so the calculation uses the unrounded daily rate to avoid losing cents.

Try this example →

Common mistakes

  • Entering the days remaining in the used-days field. The second day field is days already used; the tool subtracts it from the total.
  • Using 30 days for every month. A 31-day month has a smaller daily rate than a 30-day month for the same price, so enter the actual length of the billing period.
  • Multiplying the rounded daily rate by the days. That introduces rounding errors of a few cents; use the charge shown.
  • Expecting taxes or fees to be added. The result covers the plan price only.

Sources

  • Prorated — Corporate Finance Institute

About this calculator

This calculator works out a prorated charge as: (full period price ÷ total days in the billing cycle) × days remaining (the total days minus the days already used, which is what you enter), so a customer only pays for the portion of the period they actually use rather than the full recurring price. If someone upgrades halfway through a 30-day billing cycle, this calculation charges them for roughly 15 days at the new rate instead of a full month.

Subscription businesses use proration whenever a customer changes plans mid-cycle, adds a seat partway through a billing period, or cancels early, and billing platforms like Stripe and Chargebee apply exactly this arithmetic under the hood to keep charges fair and dispute-free.

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Comments (1)

  • Editorial team

    Billing-cycle length changes the answer more than you might expect. A plan of 120 with 12 days used leaves 18 days and a charge of 72.00 on a 30-day cycle, but on a 31-day cycle it leaves 19 days and a charge of 73.55. Check how your provider counts the day of the change before comparing figures. Which billing platform's invoice are you trying to match?

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