LOAN CALCULATOR
Estimate only. Lender underwriting, qualification, and final terms will differ. Auto loans typically run 3–7 years, student loans 10–20 years, personal loans 2–7 years. Shorter term = higher monthly payment but less total interest.
Updated May 2026 · Built by Lukáš, an architect in Prague.
Formula, assumptions, rounding & limitations
Formula
monthly rate = APR ÷ 12 ÷ 100M = P × [r(1+r)n] ÷ [(1+r)n − 1]total interest = (M × n) − Ptotal paid = M × n
Assumptions
- APR you enter is fixed for the full term and is divided by 12 for monthly compounding.
- Monthly payment is constant; term is in whole months.
- Both decimal comma (7,5) and decimal point (7.5) are accepted.
Rounding
- Monthly payment, total interest, and total paid are rounded to the nearest dollar for display.
Limitations
- Origination fees, points, prepayment penalties, late fees, and other lender charges are not modelled.
- Variable-rate loans, deferment, forbearance, income-driven repayment, and grace periods are not handled.
- Extra principal payments and bi-weekly schedules are not modelled.
- The APR shown is what you enter — comparing real loan offers requires each lender’s official APR disclosure.
- Estimate only. Lender underwriting, qualification, and final terms will differ.
What’s the difference between APR and interest rate on a loan?
Interest rate is the cost of borrowing the principal. APR also includes lender fees expressed as a yearly cost, so APR is always equal to or higher than the interest rate. Always compare loans on APR, not just rate.
Should I take a longer loan to lower the monthly payment?
The monthly payment drops, but total interest paid usually rises a lot. A 60-month vs 36-month auto loan can mean thousands more in interest. Use the calculator to see the trade-off explicitly before deciding.
Does this calculator account for extra payments?
No, this is a basic amortization calculator with one fixed payment. Extra principal payments shorten the term and reduce total interest, but the math is iterative — try different P or n values to see the effect.
What about variable-rate loans?
This tool assumes a fixed rate for the full term. For variable-rate loans (some private student loans, some personal loans), the rate can change, so the monthly payment shown is only correct for the period the rate stays fixed.