What is a loan payment calculator?
A loan payment calculator estimates a repeating monthly amount that could repay a principal over a chosen term at an interest rate you enter. This NumberMotive tool also shows total paid, total interest, an estimated payoff period and the effect of optional extra monthly payments.
The result is a planning estimate from the numbers you type. It does not offer credit, approve a loan, disclose an official APR or recommend financing.
How a loan payment is modeled here
The model is standard (classical) amortization. Interest is applied once per month to the remaining principal. The scheduled payment is sized so that principal plus interest could be repaid over the selected term when extra payments are $0.00. Extra monthly payments are added on top of that scheduled amount and reduce principal faster in this monthly worksheet.
The annual rate is a number you enter. It is converted to a monthly rate by dividing by 12. That conversion is a planning convention, not a Truth in Lending APR, a finance-charge disclosure or a lender quote.
The formulas this calculator uses
Monthly rate r = annual interest rate ÷ 100 ÷ 12
Scheduled months n = the term in months, or years × 12.
Scheduled monthly payment when r is greater than 0 and n is greater than 0:
M = P × [r(1+r)^n] ÷ [(1+r)^n − 1]
When the annual rate is 0% and n is greater than 0, M = P ÷ n. When P is $0.00, M is $0.00. When n is 0 and P is greater than $0.00, a scheduled payment is not estimated. The calculator does not divide by zero and does not return NaN or Infinity.
With extra monthly payments, each modeled month pays M plus the extra amount, or the remaining balance plus that month’s interest if that is smaller. Total paid is the sum of those payments. Total interest is total paid minus principal, not below $0.00. Interest savings is scheduled total interest minus interest paid with extras, not below $0.00.
Worked example
With a $20,000.00 loan, a 6% annual rate, 5 years and $0.00 extra, there are 60 scheduled months. The scheduled monthly payment is $386.66. Total paid is $23,199.36. Total interest is $3,199.36. The estimated payoff period is 60 months.
Adding $100.00 extra each month keeps the scheduled payment at $386.66 and shortens the modeled payoff to 47 months, with $754.98 less interest in this worksheet. Changing the amount, rate, term, unit or extra payment changes the result. None of those inputs is a loan offer.
What this calculator does not include
- Loan offers, pre-qualification, underwriting or credit approval
- Official APR, finance-charge or Truth in Lending disclosures
- Origination fees, points, insurance, taxes, escrow or late fees
- Variable rates, compounding other than monthly, or daily interest
- Biweekly, weekly or irregular payment calendars
- A recommendation of a lender, product, term or extra-payment strategy
Limitations of this calculator
- Results are estimates based only on the numbers, term unit and extra payment you enter.
- The schedule assumes a constant monthly rate and a constant extra amount.
- A 0-month or 0-year term with a remaining balance does not produce an infinite payment.
- Very large combinations are rejected when a result leaves the safe numeric range.
- Scenarios are not saved, emailed or sent to analytics.
Frequently asked questions
What is a loan payment calculator?
It estimates a repeating monthly amount that could repay a principal over a term and interest rate you enter. This NumberMotive version also shows total paid, total interest, an estimated payoff period and the effect of optional extra monthly payments. It is a planning worksheet, not a loan offer.
How is the monthly loan payment calculated?
The tool uses standard amortization. The annual rate is divided by 12 to get a monthly rate. When that rate is greater than 0%, the scheduled payment is P × [r(1+r)^n] ÷ [(1+r)^n − 1]. With $20,000.00, 6%, 5 years and $0.00 extra, the scheduled payment is $386.66.
What interest rate should I enter?
Enter the annual percentage you want to model. The calculator does not look up lender rates, convert an advertised APR or recommend a rate. 0% is valid and treats the loan as principal spread across the term with no interest.
Is the annual interest rate an official APR?
No. The field is a planning rate you type. Dividing by 12 is a monthly-model convention. It is not a Truth in Lending APR, a finance-charge disclosure or a lender quote.
What is amortization in this calculator?
Amortization here means each modeled month adds interest to the remaining principal, then a payment reduces that balance. Early payments are more interest-heavy when the rate is greater than 0%. The worksheet does not print a full month-by-month table or a graph.
How does the years vs months selector change the result?
Years multiplies the term by 12. Months uses the term as months. Five years and 60 months produce the same month count. Changing the unit without changing the number changes the timeline, so a 5-month term is not the same as 5 years.
What if the loan term is 0?
A 0-year or 0-month term is valid. A scheduled payment is not estimated while a balance remains and no extra payment is entered. The calculator does not divide by zero and does not return Infinity or NaN.
What if the interest rate is 0%?
A 0% rate is valid. The scheduled payment is the loan amount divided by the number of months. Total interest is $0.00 when extra payments are also $0.00.
What if the loan amount is $0?
A $0.00 loan is treated as already paid off. The monthly payment, total paid and total interest are $0.00, and the estimated payoff period is 0 months.
How is the estimated payoff period calculated?
With no extra payment, the payoff period equals the scheduled term. With extra payments, the worksheet applies the scheduled payment plus the extra amount each month until the balance reaches $0.00, or reports that a payoff cannot be estimated if the payment never reduces principal.
How do extra monthly payments work here?
Extra is added on top of the scheduled payment. It is not a replacement payment. $0.00 extra leaves the original schedule. A larger extra reduces modeled interest and can shorten the payoff. The tool does not tell you whether to prepay.
What if the extra payment is larger than the monthly payment?
That is allowed. The modeled month still starts from the scheduled payment, then adds the extra amount. A larger combined payment can repay the balance sooner. It is not a recommendation to overpay.
Can extra payments pay the loan off immediately?
If the first modeled payment (scheduled amount plus extra, or extra alone when there is no term) covers remaining principal plus that month’s interest, the worksheet shows a 1-month payoff. A $0.00 loan amount is shown as already paid off.
How is total interest calculated?
Total interest is total paid minus the loan amount, not below $0.00. With extras, total paid is the sum of the simulated monthly payments, including a smaller final payment when the last month does not need the full amount.
How is interest savings from extra payments calculated?
Interest savings is scheduled total interest minus interest paid with extras, not below $0.00. When extra is $0.00, savings is $0.00. Savings is not estimated when a scheduled payment cannot be calculated.
Is this result a loan offer, credit approval or financial advice?
No. It is a planning estimate from a principal, rate, term and optional extra payment you chose. It is not a loan offer, credit approval, APR disclosure, financing recommendation or financial advice.
Last reviewed August 24, 2026 (UTC).