How to Calculate Monthly Loan Payments (Formula, Examples, and Free Calculator)
How to Calculate Monthly Loan Payments (Formula, Examples, and Free Calculator)
Whether you're taking out a mortgage, financing a car, or considering a personal loan, knowing how to calculate your monthly payment — before you sign anything — is the single most important financial skill. The formula is simple math, and once you understand it, you'll never be surprised by a payment amount again.
The Monthly Loan Payment Formula
Every loan payment breaks down into three parts: principal (what you borrowed), interest (what the lender charges), and term (how long you have to pay it back). The monthly payment is calculated so that all three balance out exactly over the life of the loan.
The formula:
M = P × [r(1+r)^n] / [(1+r)^n − 1]
Where:
- M = Monthly payment
- P = Principal (the amount you borrow)
- r = Monthly interest rate (annual rate ÷ 12)
- n = Total number of payments (loan term in years × 12)
Step-by-Step Example
Let's calculate the monthly payment on a $200,000 mortgage at 6% annual interest over 30 years.
Step 1: Convert the annual rate to monthly
r = 6% ÷ 12 = 0.06 ÷ 12 = 0.005
Step 2: Calculate total number of payments
n = 30 × 12 = 360 payments
Step 3: Apply the formula
M = 200,000 × [0.005(1.005)^360] / [(1.005)^360 − 1] M = 200,000 × [0.005 × 6.0226] / [6.0226 − 1] M = 200,000 × 0.03011 / 5.0226 M = $1,199.10 per month
That $1,199/month covers both principal and interest. Early in the loan, more of each payment goes to interest. Over time, more goes to principal — that's the amortization process.
How to Use Our Free Loan Calculator
Rather than doing the math by hand every time, use the Loan Calculator — it calculates your exact monthly payment, total interest, and payoff date instantly.
You can also:
- Enter different interest rates to see how rate changes affect your payment
- Add extra monthly payments to see how much interest you save
- Download a full amortization schedule showing every payment broken down by principal vs. interest
How Extra Payments Affect Your Loan
Here's the power of extra payments on that same $200,000 / 30-year mortgage:
| Extra Monthly Payment | Interest Saved | Time Shortened |
| $0 | $0 | 0 |
| $100 | $28,239 | 4 years, 2 months |
| $200 | $49,382 | 7 years, 3 months |
| $500 | $96,206 | 13 years, 6 months |
Even $50–100/month makes a meaningful difference over 30 years. Use the extra payment calculator to run your own numbers.
What Affects Your Monthly Payment
Three factors determine your payment:
- Loan amount (principal) — The more you borrow, the more you pay monthly and in total interest
- Interest rate — Even a 0.5% difference on a 30-year mortgage can mean thousands over the life of the loan. Always compare rates.
- Loan term — A 15-year loan has higher monthly payments but far less total interest than a 30-year loan. A $200,000 mortgage at 6%:
- 30-year: $1,199/month, $231,676 total interest
- 15-year: $1,687/month, $103,788 total interest
Common Pitfalls to Avoid
- Not comparing rates: A 0.25% lower rate on a $300,000 mortgage saves ~$15,000 over 30 years
- Ignoring the total cost: A low monthly payment with a long term can cost twice as much in interest as a shorter, higher-payment loan
- Skipping the amortization schedule: Seeing how each payment splits between principal and interest helps you make better decisions about extra payments
- Not accounting for fees: Origination fees, appraisal, and closing costs add to the true cost of the loan
Use the Calculator Before You Sign
The best time to calculate your loan payment is before you apply — not after you've already committed. Use the Loan Calculator to set your budget, compare scenarios, and walk into any negotiation with clear numbers.
Related tools:
- Loan Calculator — monthly payment, amortization, extra payments
- Mortgage Calculator — for home purchase planning
- Currency Converter — for international loans or currency-adjusted payments