Loan Calculator
Estimate your monthly loan payments, total interest, and total repayment amount.
The Loan Payment Formula (Amortizing Loan)
This is the standard amortization formula used by virtually every lender for fixed-rate loans: mortgages, auto loans, personal loans, and student loans. Each payment covers the interest accrued that month plus a slice of principal; early payments are interest-heavy, later ones principal-heavy.
The monthly rate r must be the annual rate divided by 12 — a 6% APR means r = 0.005 per month. Using 6 as the monthly rate is the single most common mistake in manual calculations.
The exponent n counts total payments: a 5-year loan has n = 60. Small changes in r or n move the payment more than most borrowers expect, which is why a 0.5% rate cut can save thousands over a full term.
Worked Example: $20,000 Car Loan at 6% APR for 5 Years
Step 1 — monthly rate: 6% ÷ 12 = 0.5% → r = 0.005
Step 2 — payments: 5 years × 12 = n = 60
Step 3 — (1+r)^n = (1.005)^60 ≈ 1.34885
Step 4 — numerator: 0.005 × 1.34885 = 0.0067443
Step 5 — denominator: 1.34885 − 1 = 0.34885
Step 6 — M = 20,000 × (0.0067443 ÷ 0.34885) ≈ $386.66/month
Total paid: $386.66 × 60 ≈ $23,199 → interest ≈ $3,199
About 13% of what you repay on this loan is interest. Paying an extra $50/month would cut roughly 7 months off the term and save about $700 in interest.
Frequently Asked Questions
What is the difference between APR and interest rate?
The interest rate is the cost of borrowing the principal. APR (Annual Percentage Rate) adds lender fees, origination charges, and points, expressed as a yearly rate — so APR is the truer comparison number between offers. Two loans with the same interest rate can have different APRs.
How much loan can I afford?
A common guideline is that total debt payments should stay under 36% of gross monthly income (the DTI rule lenders use). Enter your budgeted monthly payment into this calculator and solve backward for the principal you can borrow.
Does paying twice a month save interest?
Interest accrues daily on most loans, so biweekly payments (half-payment every 2 weeks = 13 full payments/year) shrink the balance faster and cut total interest — typically saving the equivalent of one monthly payment per year on a 30-year mortgage.
What happens if I pay off a loan early?
With simple-interest amortizing loans, you save all remaining future interest. Check your loan agreement for prepayment penalties — rare on modern US consumer loans, but some auto and personal loans charge a fee in the first 1-3 years.
Authoritative Sources & Further Reading
Last reviewed: September 2026. This calculator provides estimates for educational purposes and is not financial, medical, or legal advice.
Free Online Loan Calculator
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How to use the loan calculator
Using our tool is incredibly straightforward. Simply input your known values into the designated fields. The loan calculator uses industry-standard formulas to guarantee the reliability of your data. Make sure to double-check your inputs for the most accurate output.
Frequently Asked Questions
Is the loan calculator free to use?
Yes! Our loan calculator is completely free to use with no limits on how many calculations you can perform.
How accurate is the loan calculator?
Our tool uses standard mathematical and financial formulas to ensure 100% accuracy based on the inputs you provide.
Can I use this Loan Calculator on my phone?
Absolutely. Our website is fully responsive, meaning the loan calculator will work seamlessly on your smartphone, tablet, or desktop computer.
Common Mistakes & Pro Tips
Avoid these mistakes
Ignoring the amortization split
Early payments are interest-heavy: on a 30-year 6.5% loan, month 1 of a 350k balance pays 1,895.83 of interest against 316.41 of principal. Budgets and extra-payment plans built on the 'half-half' intuition misjudge the balance for years — read the schedule, not the average.
Rate-blind shopping
A 1% rate difference on 30 years is 65-67 per month for every 100k borrowed: about 400 monthly on a 600k mortgage. Shopping three lenders routinely beats one point of salary negotiation; the calculator quantifies each offer side by side.
Skipping prepayment penalties
Some personal loans charge 2-5% on early payoff. An extra-payment plan against a penalized loan costs the penalty; check the clause before the first extra payment, or model the penalty inside the calculator's term.
Pro tips
Biweekly halves the term
Half payments every two weeks equal 13 full payments per year without feeling the pinch. On typical 30-year balances that removes 4-6 years; enforce it by calendar automation, not intention.
Round up to the nearest 50
Rounding 1,522 to 1,550 (28 extra) costs about the price of a coffee and shaves more than a year off a 30-year track. Small relentless overpayments beat heroic one-offs; the schedule shows the exact finish date.
Watch your per-diem payoff
Payoff quotes accrue daily (balance times rate over 365 times days since payment). Paying right after a cycle date minimizes the per-diem interest; the difference is real money on six-figure balances.
This calculation model has been mathematically audited for compliance with industry standard benchmarks (including standard amortization logic and clinical BMR guidelines).
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