Finwiser › Surplus calculator
Surplus calculator
Not your salary. Not your salary minus rent. The number that is genuinely free once every rupee already spoken for has left — including the bills that only arrive once a year.
Fill in six numbers. The arithmetic happens in your browser: there is no sign-up, no account, and nothing you type is sent anywhere or stored.
We have filled in an example so you can see how it behaves. Replace each number with your own, or clear them all.
Enter your monthly take-home to begin.
A month — 60–80% of the surplus. The rest is slack for the month that goes wrong: the dentist, the flight home, the repair. Committing all of it is how a SIP ends up stopped in month five.
Twelve months of that surplus, if nothing changes
—
| Month | Cumulative surplus |
|---|---|
| 1 | ₹0 |
| 2 | ₹0 |
| 3 | ₹0 |
| 4 | ₹0 |
| 5 | ₹0 |
| 6 | ₹0 |
| 7 | ₹0 |
| 8 | ₹0 |
| 9 | ₹0 |
| 10 | ₹0 |
| 11 | ₹0 |
| 12 | ₹0 |
This is a surplus tool, not an investment projection. It does not forecast returns, does not model inflation, and does not recommend any product or scheme. It is arithmetic on the numbers you type — nothing more — and it is not investment advice under the SEBI (Investment Advisers) Regulations, 2013.
Most calculators ask for your income and your expenses, and stop there. That is why their answer is wrong for eleven months and then wrong in the other direction in the twelfth.
A term-insurance premium, advance income tax, the annual school fee, the car service, the trip home at Diwali — none of these arrive monthly, and all of them are real. A ₹96,000 premium is not a ₹96,000 shock in March. It is ₹8,000 a month you were never free to invest.
So this calculator keeps them on their own line. Divide the year’s total by twelve, subtract it before the surplus, and show it leaving. The surplus that survives that subtraction is one you can actually keep.
Does arithmetic on six numbers you typed from memory. It is fast, it is private, and it is only as accurate as your estimate of “everyday spending” — which is the number almost everybody gets wrong, usually by a lot.
Reads your real accounts over India’s Account Aggregator rail — read-only, with your consent, and never your bank password — then recomputes the surplus every month from what actually happened, not from what you remembered.
Your surplus is what is left of your take-home pay after every rupee that is already spoken for has left — rent or EMI, the regular bills, everyday spending, the SIPs you are already paying, and a twelfth of the payments that only arrive once a year. It is not your salary minus your rent. It is the number you can act on without breaking something else.
A common rule of thumb is 60 to 80 per cent of the surplus. The remaining 20 to 40 per cent is slack for the month that goes wrong — the dentist, the flight home, the repair. Committing 100 per cent of a surplus is how a monthly SIP ends up being stopped in month five, which costs you more than starting smaller would have. This is a rule of thumb, not a recommendation for your situation.
Because they are real money that is simply not due this month. A ₹96,000 insurance premium is not a ₹96,000 shock in March — it is ₹8,000 a month you were never free to invest. If you leave it out, your surplus looks bigger than it is for eleven months and then collapses in the twelfth. This calculator divides the annual total by twelve and subtracts it on its own line, so you can see it leave.
No. The arithmetic runs in your browser. Nothing you type is sent anywhere, nothing is saved, and there is no sign-up. Reload the page and the example values come back — that is the proof that nothing was kept.
No. It is a surplus tool, not an investment projection. It does not forecast returns, does not model inflation, and does not recommend any product. It answers one question — how much is actually free — and that is a question of arithmetic, not of markets.
Connect once through the Account Aggregator and Finwiser recomputes this number every month from your real accounts — read-only, and never your bank password.
Android, on Google Play. Free during early access.
