Mortgage Calculator
Work out your monthly payment and see how regular overpayments or lump sums change the interest and the payoff date.
- Calculated in your browser
- Formula and rounding
- Reviewed
Monthly paymentExample
$1,169.18
300 payments
- Loan amount
- $200,000.00
- Total interest
- $150,754.02
- Total repaid
- $350,754.02
- Final payment
- $1,169.20
- Early repayment charges, prepayment penalties and overpayment allowances vary by lender. Check yours before overpaying.
- Keep an emergency fund before making overpayments.
Monthly rate: annual rate ÷ 12
i = r / 12r = 0.05
= 0.00416666…
Monthly payment (principal and interest, rounded)
PMT = P × i / (1 − (1 + i)^−n)P = 200000i = 0.00416666…n = 300
= 1169.18
Total interest (interest each month rounded to the minor unit)
Σ round(balance × i)payments = 300
= 150754.02
- Balance
$1,169.18 a month over 300 payments; total interest $150,754.02.
Assumptions
- Preset: Standard monthly (UK, IE, AU, NZ, US principal & interest).
- Rate 5% is a nominal annual rate; interest is charged monthly at rate ÷ 12 (some lenders calculate daily).
- 300 monthly payments; interest is rounded to the minor unit each month and the final payment absorbs rounding.
- No overpayments.
- The rate is fixed for the whole term.
- Fees, early repayment charges and insurance are not included unless entered.
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Estimates for general information only — not financial, tax or legal advice. Your actual figures depend on your employer’s payroll, your full tax situation, your lender’s or bank’s terms and rules we may not model. Check official sources and speak to a qualified adviser before making decisions. Disclaimer · Report an error
How to calculate a mortgage payment with overpayments
A repayment mortgage is a long loan paid back in equal monthly amounts. Each payment covers that month’s interest and pays off a slice of the balance. Because the term is long, even a small change to the rate or to what you pay each month can move the total interest by thousands.
This calculator gives you the monthly payment, the total interest and a payment-by-payment schedule. Add regular overpayments or lump sums and it shows a second line: how much sooner the mortgage ends and how much interest you avoid. A Canada preset applies the semi-annual compounding used for Canadian fixed-rate mortgages.
- 1
Enter the mortgage
Type the loan amount, or the price and your deposit. Add the rate and the term in years, then choose the Standard monthly preset (UK, Ireland, Australia, New Zealand, US principal and interest) or the Canada preset.
- 2
Add overpayments if you plan any
Enter a regular monthly overpayment and the month it starts, up to 10 lump sums, or a yearly lump sum. Choose whether overpayments shorten the term or lower the monthly payment, and set a yearly allowance if your deal has one.
- 3
Compare the two lines
The results show the payment, payoff date and total interest, then the time and interest saved. The chart plots the balance with and without overpayments, and the schedule lists every payment.
What this calculator does
- Loan amount, or property price minus deposit
- Standard monthly and Canadian semi-annual compounding presets
- Regular overpayments starting from any month
- Up to 10 one-off lump sums plus a yearly lump sum
- Reduce the term or reduce the payment after overpaying
- Yearly overpayment allowance check with a warning
- Payoff date, total interest, and time and interest saved
- Two-line balance chart, full schedule and CSV export
Worked example: 200,000 over 25 years at 5%
A 25-year mortgage, then 200 a month extra
You borrow 200,000 (any currency) at 5% a year, repaid monthly over 25 years.
| No overpayment | +200 a month | |
|---|---|---|
| Monthly payment | 1,169.18 | 1,369.18 |
| Number of payments | 300 | 226 |
| Final payment | 1,169.20 | 845.96 |
| Total interest | 150,754.02 | 108,911.46 |
In this scenario, paying 200 more each month ends the mortgage 74 payments early, about 6 years and 2 months, and avoids 41,842.56 of interest.
Canada preset: 300,000 at 5% over 25 years, compounded semi-annually, gives a monthly rate of 0.4123915% and a payment of 1,744.81. With monthly compounding at the same quoted 5%, the payment would be 1,753.77.
How it’s calculated
The monthly payment uses the annuity formula payment = L × i ÷ (1 − (1 + i)^−n), where L is the loan, i the monthly rate and n the number of months. Under the Standard preset, i = rate ÷ 12. Each month, interest is the balance times i, rounded to the smallest currency unit, and the final payment absorbs any rounding left over. Overpayments are applied after the regular payment.
Under the Canada preset, the quoted rate is compounded twice a year, so the monthly rate is (1 + rate ÷ 2)^(1/6) − 1. Canada’s Interest Act (section 6) requires a mortgage with blended payments to state the rate calculated yearly or half-yearly, not in advance. That is why the same headline 5% gives a slightly lower payment in Canada. See our methodology page for the full method.
Things to check before overpaying
- Charges and allowances vary by lender. Many fixed-rate deals allow a set amount of overpayment each year, often a percentage of the balance, and charge an early repayment charge or prepayment penalty above it. The calculator can warn you when your overpayments pass the allowance you enter for any 12-month period.
- Keep an emergency fund. Money paid into a mortgage is usually hard to get back quickly.
- Reduce-payment keeps the term. If your lender lowers your monthly payment after an overpayment, the mortgage still runs to its original end date and you save less interest than with a shorter term.
Our guide on whether to overpay the mortgage or save sets the two side by side. To model the saving option, use the compound interest calculator or the savings goal calculator. For a car or personal loan, the loan calculator uses the same schedule logic.
Good to know
- Results cover principal and interest. Property tax, insurance, mortgage insurance and service charges are extra.
- The rate is treated as fixed for the whole term. Most mortgages move to a different rate after the initial deal ends.
- Your lender may calculate interest daily or round differently, so its figures can differ slightly.
- An APR or APRC on a mortgage offer includes fees and is not the same as the rate you enter here. See our guide to APR and other rates.
What happens to the numbers you type
Your numbers stay in your browser. MoneyOtter works out your results on your device. We don’t send the amounts you type to our servers or store them. If you allow analytics, we record only broad ranges (for example “middle tax band”) to understand how the calculators are used. Like any website with ads, this page also loads advertising scripts; see our Privacy Policy.
The calculator is plain code running in this tab. It makes no network requests with your figures, and nothing is saved when you leave unless you choose to keep it. Read the privacy policy for how ads and analytics work on this site.
Related calculators and guides
Questions people ask
How is a monthly mortgage payment calculated?
With the annuity formula L × i ÷ (1 − (1 + i)^−n). A 200,000 mortgage at 5% over 25 years has a monthly rate of 5% ÷ 12 and 300 payments, giving 1,169.18 a month.
How much can I save by overpaying my mortgage?
It depends on the rate, the balance and how early you start. On 200,000 at 5% over 25 years, 200 extra a month saves 41,842.56 in interest and ends the mortgage 74 months early.
Is it better to overpay monthly or make a lump sum?
At the same rate, money paid earlier saves more interest, because it stops interest from building on that amount sooner. The calculator lets you model both to compare them in your scenario.
Why are Canadian mortgage payments calculated differently?
Canadian fixed-rate mortgages usually compound interest semi-annually, not monthly. The monthly rate is (1 + r ÷ 2)^(1/6) − 1, so 300,000 at 5% over 25 years costs 1,744.81 a month instead of 1,753.77.
Do overpayments reduce my monthly payment or my term?
It depends on your lender. Some shorten the term, some lower the payment and some let you choose. The calculator shows either option. Reducing the payment keeps the original end date.
What is an early repayment charge?
A fee some lenders charge if you repay more than your allowance or repay the whole mortgage during a fixed or discounted deal. In the US and Canada it is often called a prepayment penalty. The amount and rules vary by lender.
Does this include property tax and insurance?
The main result covers principal and interest only. Add your own estimates for taxes, insurance and fees to see the full monthly cost.
Sources and review
- Interest Act (Canada), R.S.C. 1985, c. I-15, section 6
- Financial Consumer Agency of Canada — Mortgage prepayment penalties
- CFPB — Mortgage interest rate vs APR
- CFPB — What is amortization?
Estimates for general information only — not financial, tax or legal advice. Your actual figures depend on your employer’s payroll, your full tax situation, your lender’s or bank’s terms and rules we may not model. Check official sources and speak to a qualified adviser before making decisions.
Page reviewed by the MoneyOtter team · Methodology · Changelog · Report an error