Payment Calculator

What is a Payment Calculator?

A payment calculator determines your fixed monthly payment for an amortizing loan — one where each payment covers interest and part of the principal until the balance reaches zero. It also shows the total you will pay and how much of that is interest, so you can compare offers before you borrow.

It works for any loan with a fixed rate and equal monthly payments — auto, personal, student, and fixed-rate mortgage loans. It assumes interest compounds monthly and payments are due at the end of each month.

How to Use This Calculator

1. Enter the total amount you plan to borrow.
2. Input the annual interest rate offered by your lender.
3. Choose the loan term in years or months.
4. Click Calculate to see your monthly payment, total cost, and payoff date.

The result shows the monthly payment, the total of all payments, and the total interest — the true cost of the loan above what you borrowed.

The Loan Payment Formula

Every fixed-rate amortizing loan uses the same formula:

M = P × r(1 + r)^n ÷ ((1 + r)^n − 1)

• M — the fixed monthly payment you are solving for.
• P — the principal: the amount you borrow.
• r — the monthly interest rate: the annual rate divided by 12 and by 100. A 9% annual rate becomes 0.0075 monthly.
• n — the total number of monthly payments: the term in years times 12.

When the rate is 0%, the formula simplifies to M = P ÷ n — you repay the principal in equal slices. For a month-by-month split of principal and interest, see our Amortization Calculator.

Worked Example: $15,000 Loan at 9% for 4 Years

Borrowing $15,000 at a 9% annual rate for 4 years:

• P = 15,000; r = 9 ÷ 100 ÷ 12 = 0.0075; n = 4 × 12 = 48 payments
• (1 + r)^n = 1.0075^48 ≈ 1.4314

Plugging in: M = 15,000 × 0.0075 × 1.4314 ÷ 0.4314 ≈ $373.28 per month. Over 48 months you pay $17,917.23 in total, so $2,917.23 — about 19.4% of what you borrowed — goes to interest. Enter the same values above and the calculator returns exactly these figures.

Monthly Payment Reference Table

Monthly payments on three loan sizes at four rates, for 3-year and 5-year terms:

Note that doubling the loan amount exactly doubles the payment — the formula scales linearly with principal — while stretching from 3 years to 5 years cuts the payment by about a third, but that relief is not free.

What Drives Your Monthly Payment

Loan amount

The more you borrow, the more you repay each month, in direct proportion: $30,000 at 8% for 5 years costs $608.29 per month — exactly double the $304.15 payment on $15,000 at the same terms.

Interest rate

The rate moves the payment modestly but the total cost substantially. At 5%, a $15,000 5-year loan costs $283.07 per month with $1,984.11 total interest; at 14%, $349.02 per month with $5,941.43 interest — nearly triple the interest for a payment only $66 higher.

Loan term

A longer term spreads the same debt over more payments, so each payment shrinks — but the balance accrues interest every extra month, so total interest always grows with the term even at the same rate.

Fixed vs. Variable Interest Rates

With a fixed rate, your rate and payment never change — the formula above gives one number you can budget around for years. With a variable (adjustable) rate, the rate tracks a benchmark index, resets periodically, and your payment is recalculated at each reset. Variable rates usually start lower, which can pay off if you repay quickly or rates fall — but rising rates can push the payment well beyond the initial figure. When comparing offers, model a variable loan at several possible rates.

Three Ways to Lower Your Monthly Payment

If a loan quote does not fit your budget, you have three legitimate levers. Each uses the $15,000, 9%, 4-year baseline from above ($373.28 per month, $2,917.23 total interest).

1. Extend the loan term

Stretching the same loan to 6 years drops the payment to $270.38 — over $100 less per month. The cost: total interest climbs to $4,467.58, an extra $1,550.35. A longer term cuts a payment fastest but is the most expensive over time.

2. Qualify for a lower rate

Keeping the 4-year term but improving the rate from 9% to 6% lowers the payment to $352.28 and total interest to $1,909.22 — saving $1,008.01. Better credit, a co-signer, a larger down payment, or multiple lender quotes can all move the rate.

3. Borrow less

Reducing the loan to $12,000 (a bigger down payment or cheaper car) drops the payment to $298.62 and total interest to $2,333.78 — you save on the payment and the interest, proportionally.

The clear winners, when available, are a lower rate and a smaller loan — both cut the payment and the total cost. Extending the term is the last resort.

Frequently Asked Questions