Subscription Proration & Upgrade/Downgrade Calculator
Calculate exact prorated credits and charges when upgrading or downgrading subscription plans mid-cycle. Free interactive SaaS billing calculator.
Calculated Results
Net Due Immediately
$25.00
Unused Credit (Old Plan)
$20.00
Remaining Charge (New)
$45.00
About this tool
When a subscriber switches plans in the middle of a billing cycle—such as upgrading from a $30/mo Starter plan to a $90/mo Pro plan on day 15 of a 30-day month—proper accounting requires calculating exact prorations. Under standard subscription proration mechanics, the customer receives an unused credit balance for the unconsumed portion of their old plan (15 days = $15 credit) and is billed for the remaining days on their new plan (15 days = $45 charge), resulting in a net immediate charge of $30. Calculating prorations accurately prevents customer billing confusion, eliminates support tickets, and maintains clean revenue recognition across billing systems. Use this tool to compute prorated charges or credit balances for any mid-cycle plan adjustment.
How It Works
- 1Input the previous monthly plan price and new plan price.
- 2Input total days in the current billing cycle (typically 30 or 31).
- 3Input the number of days remaining in the billing period at the time of change.
- 4Inspect the unused credit from the old plan, the new charge for remaining days, and the net prorated amount due immediately.
Formula & Math
Transparent LogicNet Due = (New Price × (Remaining Days / Cycle Days)) - (Old Price × (Remaining Days / Cycle Days))
Worked Practical Example
A customer paying $40/mo upgrades to an $80/mo tier with 10 days remaining in a 30-day billing cycle.
Calculation / Steps
Fraction = 10 / 30 = 0.333. Unused old credit = $40 × 0.333 = $13.33. New charge = $80 × 0.333 = $26.67. Net Due = $13.34.
Expected Result
Net immediate charge of $13.34 (customer credited $13.33 for old plan; billed $26.67 for new plan).
Frequently Asked Questions
What happens if a customer downgrades mid-cycle?+
If the old plan was more expensive, the unused credit exceeds the new charge, resulting in a negative net due (a credit balance applied to future invoices).
Should prorations be applied immediately or on the next invoice?+
Upgrades are almost always charged immediately. Downgrades typically take effect at the start of the next billing cycle to avoid issuing complex mid-cycle cash refunds.
How do Stripe and Dodo Payments handle prorations?+
Both platforms have native proration engines that compute second-by-second prorations automatically unless explicitly disabled in API calls.
Automate retention on your cancel button
When users downgrade through BoolBul's cancellation flow, prorated balances are handled seamlessly by your underlying billing provider.
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