Proration Calculator
Pick what happens part way through a billing period, enter the dates and the price. You get the daily rate, what to charge or credit, and for a plan change the amount due.
The day the next period starts.
For a full period.
For a full period.
- 15 days before the date
- 15 days from the date on
- $49.00 × 15 ÷ 30= $24.50 credit
- $99.00 × 15 ÷ 30= $49.50 charge
- $49.50 − $24.50= $25.00 net
A prorated amount is the price times the share of the period it covers.
daily rate = price ÷ days in the period
prorated amount = daily rate × days charged
The calculator's period runs from 1 April 2027 to 1 May 2027, which is 30 days. A $99 plan is $3.30 a day. From 16 April 2027 there are 15 days left, so a plan that starts that day costs $49.50 for the rest of the period.
$99 for 15 of 30 days
A plan change credits the old plan's unused days and charges the same days on the new plan.
credit = old price × days left ÷ days in the period
charge = new price × days left ÷ days in the period
due now = charge − credit
A customer on the $49 plan who moves to $99 on 16 April 2027 has paid for 15 days they will not use: $49 × 15 ÷ 30 is a $24.50 credit. The same 15 days on the new plan cost $49.50. The difference, $25.00, is what the change costs.
$49 to $99 with 15 of 30 days left
Stripe's documentation gives the same sum: a customer moving from a 10 USD monthly plan to a 20 USD one halfway through the period gets a 5 USD credit and a 10 USD charge, and pays 5 USD.
The same number of days costs more in a short month than in a long one.
Prorating by the day divides by the length of the period, and months run from 28 to 31 days. 10 days of a $99 plan cost $35.36 in a 28-day February and $31.94 in a 31-day month.
The daily rate of a $99 plan by period length
A downgrade leaves a credit instead of a charge.
Turn the example around: a customer moves from $99 to $49 on 16 April 2027. The credit for the unused 15 days is $49.50, the charge for the cheaper plan $24.50, so the customer is owed $25.00.
On Stripe, that credit is not paid back on its own. Its documentation says "negative prorations aren't automatically refunded and positive prorations aren't immediately billed, although you can do both manually."
Stripe prorates to the second, and one setting decides when the customer pays.
Stripe's documentation says "by default, Stripe calculates prorations down to the second", so a change in the afternoon prorates part of that day, and its figure can differ from a whole-day count by a few cents. When it prorates, it uses "the subscription's discounted price, not the original price". When the proration is billed depends on the proration_behavior setting.
| Setting | What Stripe does |
|---|---|
| create_prorations (the default) | Creates proration invoice items when applicable. They are only invoiced immediately under certain conditions. |
| always_invoice | Calculates the proration, then immediately generates an invoice. |
| none | No proration. The customer is billed the full new price when the next invoice is generated. |
Read the details in Stripe's guide to prorations.
Source: Stripe Docs, "Prorations", read 16 October 2026.
Upgrades are expansion revenue, and the MRR and ARR calculator shows how they move MRR. For a price change across all customers, use the price increase calculator. 1Capture collects the first payment in the last 2 hours of a trial and retries it up to 10 times if it fails, as the payment capture page explains.
People also ask these questions about proration.
How do you calculate a prorated amount?
Divide the price by the number of days in the period to get a daily rate, then multiply by the days you are charging for. A $99 plan in a 30-day period is $3.30 a day, so 15 days cost $49.50.
How is a subscription upgrade prorated?
The customer gets a credit for the unused days of the old plan and a charge for the same days of the new one, and pays the difference. Moving from $49 to $99 with 15 of 30 days left credits $24.50, charges $49.50, and leaves $25.00 to pay.
What happens when a customer downgrades mid-period?
The credit for the old plan is larger than the charge for the new one, so the customer is left with a credit. From $99 to $49 with 15 days left, the credit is $49.50 and the charge $24.50, a credit of $25.00. Stripe says negative prorations are not refunded automatically.
Does Stripe prorate by the day?
Not by default. Stripe's documentation says "by default, Stripe calculates prorations down to the second", and that you can change the granularity to a day, hour, week or month with proration customizations (Stripe Docs, "Prorations", read 16 October 2026). A day-based figure can differ from Stripe's by a few cents.
Do you count the day of the change?
This calculator counts from the start date up to, but not including, the next billing date, the way a billing period runs. 1 April 2027 to 1 May 2027 is 30 days, and a change on 16 April 2027 leaves 15 days, the change day included.
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