Subscription Proration Calculator
The mid-cycle split — upgrade or cancel and the unused days carry a credit, the used days carry a charge, priced to the day.
Subscription Proration Calculator
Results recalculate instantly on every keystroke. Nothing you type is transmitted.
What this result does not account for
- Plan 0.01 to 100,000; cycle 1 to 366 days
- Daily proration priced — keep-full-cycle and credit-only policies named as the terms' alternatives
In short: Cancel a $15 monthly plan 12 days in: 12 days were used, 18 were not — the credit is $9.00 at fifty cents a day. Upgrade mid-cycle and the same split runs both plans: the old plan's unused days credit, the new plan's remaining days charge, and the difference is the honest invoice. Same arithmetic as the lease's partial month — different contract, and this one usually names its own method in the terms.
Formula
credit = plan ÷ period × unused · upgrade due = new ÷ period × remaining − credit
A cycle is days at a price; leave early and the price splits at the day you left. Used days keep their charge — the service existed. Unused days carry a credit at the plan's own daily rate, which is where policies differ: daily proration is the honest default, but some terms keep the whole cycle, some round to weeks, some pay in credit only. The upgrade runs the split twice — the old plan credits its remainder, the new plan charges its — and the difference is what the invoice should say. The terms you signed name which of these the company actually does.
Worked Example
- Enter the plan price and the cycle length.
- Say how many days of the cycle you used.
- Read the credit — or the upgrade's true invoice.
Defaults: $15 over 30 days, 12 used — 18 unused, $9.00 credit at $0.50 a day; leave the new-plan field empty to read the cancel case.
Strengths & Limits Of This Model
Where this engine is strong
- Cancel and upgrade in one grid
- Negative amounts read signed
- The daily rate printed beside the split
Where it stops
- Prices daily proration — the terms govern what is actually paid
Practical Use Cases
Cancellations
the unused days priced
Upgrades
the honest mid-cycle invoice
Refund checks
the daily rate, verified
Methodology & Editorial Standards
Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.
This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.
Disclaimer. This calculator is provided for informational and modelling purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Verify all figures with a qualified professional before acting on them.
Subscription Proration Calculator — 8 Expert FAQs
8 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
How do I prorate a cancellation?
Price the cycle by the day and pay for the days used: $15 over 30 days is $0.50 a day, so cancelling with 18 days unused carries a $9.00 credit. Whether you receive cash or account credit is the terms' decision — the size of it is arithmetic.
How does a mid-cycle upgrade work?
Two splits on one day: the old plan credits its unused days, the new plan charges its remaining days. A 12-day upgrade from $10 to $15 over a 30-day cycle credits $4.00 and charges $9.00 — $5.00 due now. The card prints both lines so the invoice can be checked.
What if I was overcharged mid-cycle?
Enter what the plan should cost and what was charged in the upgrade field: a $15 plan charged $12 is $3.00 owing TO you — the card prints negative amounts signed, the direction named. Screenshot the math before the support ticket.
Do all services prorate?
No — plenty keep the full cycle on cancel, round changes to whole weeks, or pay credits instead of cash. The daily split here is the honest default and the comparison baseline; what you signed decides which column the money lands in.
Does the cycle length matter that much?
It sets the daily rate: $15 over 30 days is $0.50 a day, over 31 it is $0.4839, over 28 it is $0.5357. Eleven unused days swing over a dollar between a 30- and 31-day cycle — enter the real one, and February's 28 is its own honest arithmetic.
What about annual plans?
The arithmetic does not care about the label: price divided by days in the term, times unused days. A $120 annual plan is 33 cents a day; the card reads the same. Whether an annual refund is offered at all is the terms' business.
Why does the used side never refund?
Because the days happened — the service ran and the charge earned. Proration splits time, it does not judge it; only a goodwill policy or a broken service hands back the used days, and those are not arithmetic.
Is this the same math as prorated rent?
Identical to the day — price over period times days held. The difference is contractual: rent proration lives in a lease clause, subscription proration in terms of service, and the two pages name their own contracts while sharing the arithmetic.