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CALCPARK

Loan Calculator

Monthly payment, total interest and a full amortization schedule for any fixed-rate loan in any currency. Add fees for the APR, or an extra payment to see what you save.

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How to use it

  1. Enter the amount borrowed, the yearly interest rate as quoted (not the monthly rate) and the term in years or months.
  2. Read the monthly payment, total interest and total paid. The bar shows how much of all payments is interest.
  3. Optional: add an extra monthly payment to see the interest saved and how much sooner the loan ends, or enter the lender’s fees to get the APR.
  4. Open the amortization schedule by year or by month, or download it as CSV for a spreadsheet.
  5. Copy the summary or the link – the link carries every input, so you can send a scenario to someone else.

Example

Amount 200,000, rate 6%, term 30 years. Monthly rate r = 0.06 ÷ 12 = 0.005 and n = 360, so M = 200,000 × 0.005 × 1.005³⁶⁰ ÷ (1.005³⁶⁰ − 1) = 1,199.10. The first payment contains 1,000.00 interest (200,000 × 0.005) and only 199.10 principal; by the last year the split is reversed. With a 4,000 fee deducted at disbursement the borrower receives 196,000 but still pays 1,199.10 for 360 months, which is an APR of 6.19%. Paying 1,399.10 instead (200 extra) finishes after 252 payments and costs 151,875.87 in interest instead of 231,676.38.

Formulas and assumptions

The payment is the standard annuity formula for a fixed-rate loan with equal monthly instalments:

M = P × r × (1 + r)ⁿ ÷ ((1 + r)ⁿ − 1)      r = yearly rate ÷ 12,  n = number of months
M = P ÷ n when the rate is 0

Each month the interest is the remaining balance × r; the rest of the payment reduces the balance. An extra payment is applied to the balance in the same month, which is why it shortens the term instead of lowering the instalment (the usual bank treatment unless you ask for a recalculation). The last payment is trimmed so the balance ends at exactly zero.

APR

The APR is the rate that makes the present value of everything you pay (instalments plus any monthly fee) equal to what you actually receive (principal minus any up-front fee). The tool solves this by bisection on the monthly rate i*:

P − upfront fee = Σ (M + monthly fee) ÷ (1 + i*)ᵏ   for k = 1 … n
APR (nominal, US Regulation Z style) = i* × 12
Effective annual rate (EU APRC / APY style) = (1 + i*)¹² − 1

Both figures are shown because disclosure rules differ: US lenders quote the nominal APR (6.19% in the example), EU and UK lenders quote the compounded APRC, which is higher (6.37% for the same loan). With no fees the APR equals the interest rate exactly.

Limits

  • Fixed rate, monthly payments, interest compounded monthly. Variable rates, daily-interest or bi-weekly products differ.
  • Fees other than the two you enter (insurance, valuation, legal fees) are not included; a lender’s official APR may be higher.
  • No payment holidays, balloon payments or interest-only periods. Terms up to 50 years (600 payments).

Sources: Wikipedia – Amortization calculator (annuity formula), Consumer Financial Protection Bureau – What is an APR?, EU Consumer Credit Directive 2008/48/EC, Annex I – APRC formula.

This is an estimate for planning and comparison. Your lender’s contract, rounding rules and fee list decide the real payment and APR; always check the official offer before signing.

How the term changes the cost

The same 200,000 at 6% costs 1,687.71 a month over 15 years but only 103,788 in interest – less than half the 30-year figure. A longer term lowers the instalment and raises the total cost; the schedule makes the trade-off visible year by year, and the extra-payment field shows a middle way: keep the long term for safety, pay more when you can.

Questions

How is the monthly payment calculated?
With the annuity formula M = P·r·(1+r)ⁿ ÷ ((1+r)ⁿ − 1), where P is the amount, r the yearly rate divided by 12 and n the number of months. For 200,000 at 6% over 30 years that gives 1,199.10.
What is the difference between the interest rate and the APR?
The interest rate prices only the money borrowed. The APR also spreads the fees over the term, so it is the better number for comparing offers. Without fees the two are identical.
Does an extra payment lower my instalment or shorten the loan?
Here it shortens the loan: the extra amount reduces the balance, so less interest accrues and the final payment comes sooner. Some lenders will instead recalculate a lower instalment on request.
Can I use this for a mortgage, car loan or personal loan?
Yes – any fixed-rate loan repaid in equal monthly instalments. Enter the term in months for short loans (for example 48 months for a car) and in years for mortgages.