Otaku Dojo Tools
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Loan Calculator

The Loan Calculator works out the monthly payment, total interest and total repaid for a loan from its amount, annual interest rate and term. Choose level payments (the same amount every month) or equal principal (fixed principal with falling interest), add an interest-only period, and see a year-by-year amortization table with a downloadable monthly CSV.

  • Free
  • No sign-up
  • Runs in your browser
Options
Repayment
Result
The result will appear here
Results appear as you type

How to use the Loan Calculator

  1. Enter the loan amount, annual interest rate (%) and term in years.
  2. Choose level payments or equal principal repayment.
  3. Add an interest-only period if your loan has one.
  4. The monthly payment, total interest and yearly schedule appear instantly; press "Download" for the monthly CSV.

Examples

$300,000 mortgage at 6.5% for 30 years

Input
300,000 | 6.5% | 30 years | level payments
Output
Monthly payment: 1,896
Total interest: 382,633

Same loan with equal principal repayment

Equal principal costs more at the start but saves about 89,000 in interest.

Input
300,000 | 6.5% | 30 years | equal principal
Output
First payment: 2,458
Total interest: 293,313

Level payments vs. equal principal

Level payments (a standard amortizing loan) keep the monthly payment the same; early payments are mostly interest. Equal principal repays the same principal each month, so interest — and the payment — falls over time and total interest is lower.

An interest-only period lowers payments at first, but because the balance does not shrink, payments rise afterwards and total interest goes up.

Specs & key facts

Repayment typesLevel payments, equal principal
InterestMonthly rate (annual rate ÷ 12), compounded monthly
Interest-only period0–10 years
OutputMonthly payment, total interest, total cost, yearly schedule, monthly CSV
Use forMortgages, personal loans, car loans with a fixed rate
NoteEstimates only; lenders may calculate interest daily or add fees

FAQ

My mortgage rate is variable. Is this still useful?

The calculator assumes a fixed rate. When your rate changes, enter the remaining balance and remaining term to estimate the new payment.

Does an interest-only period save money?

No. It lowers early payments, but the balance does not fall during that time, so total interest increases.

How much do extra payments save?

Principal you repay early stops accruing interest, so earlier is better. Enter the remaining balance and term to compare total interest before and after.

Why is my lender's figure slightly different?

Lenders may use daily interest, different rounding, or include insurance and fees. Use their official figures for decisions.