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Flat Rate Loan Calculator : Flat Interest Calculation & Payment

In a flat rate loan, interest is calculated on the original full principal amount for the entire tenure, without reducing as you make payments. Use this calculator to see your exact flat monthly installment.

Interactive Calculator

100% Client-Side Engine
%
yrs
Flat Monthly Payment
$344.44 / mo
Original Principal
$10,000
Total Flat Interest
$2,400
Total Repayment Amount
$12,400

Step-by-Step Examples

$10,000 at 8% Flat Rate for 3 Years

Flat interest loan computation.

Inputs: Principal: $10,000, Flat Rate: 8%, Term: 3 Years
Result: Monthly Payment: $344.44, Total Interest: $2,400.00, Effective APR: ~14.55%

Total interest is fixed at $2,400 ($800/yr for 3 yrs), making the effective APR almost double the flat rate.

How to Use This Tool

  1. Enter initial principal amount.
  2. Enter flat annual interest rate percentage.
  3. Specify loan term in years.
  4. Calculate flat monthly payment, total interest, and effective APR.

Frequently Asked Questions

Because flat interest charges interest on the full original principal for the entire loan life, even after you have paid off most of the balance.