doomath Calculator
Loan Payoff Calculator
Estimate the months and years required to repay a loan from its balance, rate and payment.
InputsChange a value to recalculate instantly
ResultUpdates as you type
FORMULA & STEPSLoan Payoff Calculator — Mathematical Derivation & Steps
3 StepsSequential Calculation Breakdown
1
Monthly rate
Convert the annual rate to a monthly rate.
2
Check amortization
A payment below this amount will not repay the loan.
3
Solve payments
The estimate assumes a constant rate and payment.
λ DooMathWork with this calculation
Local · deterministic · optionalQuick mathNatural-language-style shortcuts for deterministic arithmetic.
Calculator guide
How to use the Loan Payoff Calculator
Estimate the months and years required to repay a loan from its balance, rate and payment.
01Set inputsChoose values, units and assumptions.
02Apply the modeln = −ln(1 − P×r/payment) ÷ ln(1+r).
03Read the resultCheck the output against the assumptions before using it.
What this calculator does
Solve the fixed-payment amortization equation for the remaining number of payments.
Formula & method
n = −ln(1 − P×r/payment) ÷ ln(1+r).
Assumptions & notes
- The payment must exceed monthly interest for payoff to occur.
