Calculator
Loan Payment Calculator: Estimate Monthly Cost and Total Interest
Estimate installment loan payments using principal, APR, and term length with quick side-by-side comparisons.
Overview
Loan payment calculator: estimate a monthly payment in seconds
This calculator estimates a fixed-rate installment-loan monthly payment using the standard amortization formula. It is useful for personal loans, auto loans, and any other fully-amortizing fixed-rate product where the term is expressed in months.
Loan payment results
Formula
The math behind the calculator
The monthly payment P on a loan of amount A, monthly rate r (annual APR ÷ 12), and term n months is:
P = A · r ÷ (1 − (1 + r)−n)
This is the same closed-form amortization formula used by every standard lender quoting tool. It assumes a fixed rate over the full term and no fees added to the monthly payment. Fees that come out of the loan’s proceeds at funding (origination fees) reduce the cash you receive but do not change the calculated monthly payment for the requested amount.
Example
Worked example
A $20,000 personal loan at 9.0% APR over 48 months produces a monthly payment near $498. Total interest over the life of the loan is roughly $3,894. Move the rate to 12% and the payment rises to about $527 with total interest near $5,275 — a single rate change adds more than a thousand dollars in total cost on the same loan amount.
Limits
What this calculator cannot tell you
The calculator does not estimate approval odds, does not account for variable rates, does not include lender fees in the APR, and does not adjust for credit profile. Use it for “is this payment realistic?” planning, then verify the final terms on a lender’s firm offer or Loan Estimate.
FAQ
Common questions
Does the calculator account for origination fees?
Not directly. To capture fees, calculate the payment for the full loan amount the lender quotes, then divide total interest by the cash you actually receive at funding (loan amount minus origination fee) to compare offers fairly.
Can I use this for an auto loan?
Yes. Use the loan amount net of down payment and trade-in. For an apples-to-apples lender comparison, include any dealer-financed fees in the loan amount or in your manual cost calculation.
Why does my actual quote differ?
Lenders may round, apply different day-count conventions, or include fees in different places. The calculator’s result is a planning estimate that should match within a few dollars of a fee-free quote.
Sources & Methodology
Where we pulled the numbers
- CFPB · Personal loans explained — Plain-language CFPB explainer on how personal loans work, what fees to expect, and consumer protections.
- Federal Reserve · G.19 Consumer Credit release — Official monthly consumer credit data used for APR and balance context.
- FTC · Personal loan scams — Plain-English FTC guidance on what to watch for when shopping for a personal loan.
This guide was created with AI-assisted drafting and human editorial review by Javi Pérez. Figures, examples, and explanations are checked against public sources including CFPB, the Federal Reserve, FDIC, BLS, FTC, and SEC where applicable. Content is reviewed quarterly. Javi Pérez is not a licensed financial advisor, CPA, CFP, loan officer, tax professional, or attorney. This content is educational only and does not replace advice from a qualified professional.
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