Loan Calculator
Calculate the monthly payment, total interest and full amortisation cost of any fixed-rate instalment loan, and see how much a little extra each month actually saves you.
Loan Calculator
Results recalculate instantly on every keystroke. Nothing you type is transmitted.
What this result does not account for
- Results are a model, not a quotation — an institution's own figures govern.
- Every input is an assumption; change one and the answer changes with it.
- Rounding is applied only at the display layer, so totals may differ by a cent from a statement that rounds each line.
In short: A fixed-rate loan payment is calculated as M = P·i(1+i)^n / ((1+i)^n − 1), where P is the amount borrowed, i the monthly rate (annual ÷ 12) and n the number of monthly payments. The payment stays constant, but the split between interest and principal shifts toward principal over time.
Formula
M = monthly payment · P = principal · i = monthly rate · n = number of payments
Worked Example
- Find the monthly rate. 7.5% ÷ 12 = 0.00625.
- Count the payments. 5 years × 12 = 60 payments.
- Apply the formula. M = 25,000 × 0.00625(1.00625)60 ÷ ((1.00625)60 − 1) = $500.95.
- Total the repayment. $500.95 × 60 = $30,056.92.
- Isolate the interest. $30,056.92 − $25,000.00 = $5,056.92.
Analyst's note. Interest equals 20.2% of the amount borrowed on these terms. The first payment alone carries $156.25 of interest; by the final payment that has fallen to almost nothing, which is why early extra payments are so much more powerful than late ones.
Strengths & Limits Of This Model
Where this engine is strong
- Runs entirely in your browser — no figure you type is transmitted or stored.
- Shows the full working, so every number can be traced and challenged.
- Free, unmetered and free of affiliate incentives.
Where it stops
- Generalised assumptions cannot capture every individual circumstance.
- Jurisdiction-specific rules and mid-year changes may not be reflected.
- A model output is not a substitute for a professional review of your position.
Practical Use Cases
Comparing competing loan offers
Never compare loans on monthly payment alone — a longer term always lowers the payment while raising the total cost. Compare total interest at equal terms, and check the APR Calculator to fold origination fees into the true rate.
Deciding whether to overpay
Enter a trial figure in the extra payment field. Because extra money attacks principal directly, it removes every future interest charge that principal would have generated. The saving is almost always larger than people expect — see the Debt Payoff Calculator for multi-debt strategies.
Checking affordability before applying
Lenders assess your debt-to-income ratio, not just the payment. Model the payment here, then confirm it against your income with the Personal Loan Affordability Calculator before submitting a formal application that triggers a hard credit check.
Methodology & Editorial Standards
This engine uses the standard annuity payment formula for fixed-rate, fully amortising loans, then simulates the actual payment schedule period by period so that extra payments, early payoff and true total interest are computed from the real balance path rather than a closed-form approximation. Payments are assumed to be made on schedule at the end of each period. The engine implements the standard published formula for this calculation. Inputs are validated for domain and sign before evaluation, and any undefined case returns an em-dash rather than a spurious value.
Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.
This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.
Disclaimer. This calculator is provided for informational and modelling purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Verify all figures with a qualified professional before acting on them.
Loan Calculator — 20 Expert FAQs
20 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
How is a monthly loan payment calculated?
The amortising payment formula is M = P·i(1+i)^n / ((1+i)^n − 1). It solves for the constant payment that exactly retires the principal and all accrued interest over n periods. Every payment covers the interest accrued that month first, with the remainder reducing the balance.
Why is so much of my early payment interest?
Interest is charged on the outstanding balance, which is at its highest at the start. On a $25,000 loan at 7.5%, the first payment carries $156.25 of interest out of $500.95. As the balance falls, the interest portion shrinks and the principal portion grows — this is amortisation.
Does a longer loan term save me money?
No. A longer term lowers the monthly payment but increases total interest, because you are borrowing the money for longer. Judge affordability on the payment, but judge cost on total interest.
How much does an extra payment really save?
More than most people expect, because each extra dollar of principal removes all the future interest that dollar would have accrued. Enter a figure in the extra payment field to see both the interest saved and the number of months removed from the term.
What is the difference between interest rate and APR?
The interest rate prices the borrowing alone. APR additionally includes origination fees and mandatory charges, expressed as an annual rate, so it is the fairer basis for comparing offers from different lenders.
Does this calculator include fees or insurance?
No. It computes principal and interest only. Origination fees, payment protection insurance and late charges are excluded, so your lender's total cost figure may be higher.
What is a simple-interest loan?
One where interest accrues daily on the outstanding balance rather than being computed monthly. Paying early in the month reduces interest slightly; paying late increases it. Most instalment loans in the US are simple-interest loans quoted on a monthly amortisation schedule.
Can I pay off a loan early?
Usually yes, but check for prepayment penalties, which are more common on longer-term and subprime loans. Where no penalty applies, early payoff is almost always financially advantageous.
What credit score do I need?
It varies by lender and product, but the rate you are offered is strongly score-driven. A difference of even two percentage points on a $25,000 five-year loan changes total interest by well over $1,000, so improving a borderline score before applying is often worth the delay.
Why does my lender's payment differ by a few cents?
Rounding convention. Some lenders round the payment up to the nearest cent each period and adjust the final payment; others round the whole payment up to the nearest dollar. The difference is immaterial over the life of the loan.
Should I choose a secured or unsecured loan?
Secured loans are cheaper because collateral reduces the lender's risk, but you can lose the asset on default. Unsecured loans cost more and rely on your credit standing alone. Price both before deciding.
What is the daily interest cost shown?
It is the current balance multiplied by the monthly rate, divided by the average days in a month (30.44). It is a useful intuition check: it tells you what carrying the debt costs you every single day.
Is this loan calculator free to use?
Yes. It is free, requires no account, and has no usage limits. ApexConverter is funded by contextual advertising, never by selling user data.
Is my data sent to a server?
No. The engine runs as Vanilla JavaScript inside your browser under our Zero-Server Client-Side Execution model. Your figures are computed locally and are never transmitted, logged, or stored.
How accurate is this calculator?
It applies the standard closed-form formula in IEEE-754 double precision, rounding only at the display layer. The engine is reconciled against an independent reference implementation before release.
Does it work on mobile?
Yes. The interface is mobile-first with numeric keypad hints and is tested down to a 320-pixel viewport with no horizontal scrolling.
Can I use it offline?
Largely, yes. Because computation is client-side, the page continues to calculate without a network connection once it has loaded.
Which currency does it use?
Amounts display in US$ accounting format, but the underlying mathematics is currency-agnostic. The result is identical in any currency, so simply read the figures in your own.
Why does a result show an em-dash?
An em-dash indicates the calculation is not defined for the inputs given — typically a division by zero or a value outside the valid domain. We show a dash rather than a misleading number.
How do I report an error?
Email apexconverter.praxiscalc@gmail.com with the tool URL, your exact inputs, the output received and the output you expected. Verified mathematical errors are patched within 72 hours.