Loan payment calculator
Calculate monthly payments, total interest and amortization for personal loans, auto loans and more.
What is a loan calculator?
A loan calculator works out the fixed monthly payment for any installment loan — auto, personal, student — using the standard amortization formula. It also reveals what most people miss: how much interest you'll pay in total, and how dramatically an extra $25-50/month can shrink that number.
The full breakdown.
| Year | Principal paid | Interest paid | Remaining | Interest share |
|---|---|---|---|---|
| Y01 | $4,282 | $1,730 | $20,718 | 29% |
| Y02 | $4,614 | $1,397 | $16,104 | 23% |
| Y03 | $4,972 | $1,039 | $11,132 | 17% |
| Y04 | $5,358 | $653 | $5,774 | 11% |
| Y05 | $5,774 | $237 | $0 | 4% |
The installment formula behind every loan payment.
All fixed-payment installment loans — personal, auto, student — use the same annuity formula. It calculates the payment that, when repeated for every period, exactly repays both principal and interest by the final due date.
In the early months almost all of your payment is interest. As the principal falls, less interest accrues each period and more of your payment chips away at the balance. The amortization table in the calculator shows this shift month by month.
- PMT
- Monthly payment — the fixed amount due each period
- PV
- Present value — the original loan amount (principal)
- r
- Monthly rate — annual interest rate divided by 12
- n
- Total payments — loan term in years multiplied by 12
Six ways to actually use these numbers.
Compare total interest, not monthly payment.
A 7-year loan looks cheaper monthly but costs thousands more in interest. Always compute lifetime cost.
$50 extra/month is real money.
On a 5-year, $25K loan at 8.5%, $50/mo extra saves ~$400 in interest and shortens payoff by 5 months.
Rate matters more than you think.
A 1% rate difference on a $30K loan over 5 years is ~$800 in interest. Shop with three lenders minimum.
Avoid 'add-on' interest.
Some subprime auto loans use add-on interest, which doesn't decrease as principal does. Always confirm 'simple interest' or 'amortizing'.
Refinance when rates drop 1%+.
If a refi can drop your rate by a full point or more and you'll keep the loan a while, the math usually works. Run both scenarios here.
Watch the prepayment penalty.
Some loans charge a fee for early payoff. Read the disclosure before assuming extra payments are free.