Mortgage Repayment
Calculator
Calculate your home loan repayments, total interest, and payoff timeline instantly, with amortization breakdown, extra repayment impact, and offset account modelling.
| Year | Principal paid | Interest paid | Remaining balance |
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Mortgage Repayment Calculator: Calculate Your Home Loan Easily
Buying a home is the largest financial commitment most people will ever make, and understanding your monthly mortgage repayment before signing is essential to making a confident, sustainable decision. This free mortgage repayment calculator computes your exact monthly payment, total interest paid over the life of the loan, full amortization schedule, and the impact of extra repayments, giving you a complete picture of your home loan from first payment to last.
Quick example: A $400,000 home loan at 5.5% interest over 30 years costs $2,271/month in repayments. Total interest paid: $417,600, more than the original loan amount. Adding just $300 extra per month reduces total interest by approximately $115,700 and cuts 7.2 years off the loan. Use the calculator above with your actual figures for an instant, personalised result.
How the Mortgage Repayment Calculator Formula Works
This calculator measures the fixed periodic payment that fully amortizes a loan over a set number of periods, meaning the balance reaches exactly zero at the end of the term if every payment is made on schedule. It’s called an annuity (EMI) formula because it solves for one constant payment amount that works across the whole loan, even though the split between interest and principal within that payment shifts every period.
Monthly Mortgage Payment Formula (EMI):
P = L × r × (1 + r)^n / ((1 + r)^n − 1)
Where:
L = Loan principal (amount borrowed)
r = Periodic interest rate (annual rate ÷ payments per year)
n = Total number of payments (years × payments per year)
L is your loan principal. r is your annual rate divided by however many payments you make per year (12 for monthly, 26 for bi-weekly, 52 for weekly). n is your total number of payments across the full term. If you enable extra repayments, a lump sum, an offset balance, or an interest-only period, the calculator layers an additional month-by-month simulation on top of this same formula rather than changing it, which is how it can model those features without a second calculation engine.
Step-by-step calculation walkthrough
Step 1: Identify the inputs. Loan principal: $325,000. Annual interest rate: 6.25%. Loan term: 20 years (240 monthly payments).
Step 2: Apply the formula. Monthly rate = 6.25% ÷ 12 = 0.5208%. P = 325,000 × 0.005208 × (1.005208)^240 ÷ [(1.005208)^240 − 1].
Step 3: Perform the calculation. Working through the exponents gives a monthly payment of $2,375.52. Over 240 payments, total repayment comes to $570,125, of which $245,125 is interest and $325,000 is the original principal.
Step 4: Interpret the result. This $325,000 loan costs $2,375.52 a month for 20 years straight, with the amount never changing on a fixed rate. Total interest of $245,125 works out to about 75% of the amount borrowed, lower than a 30-year loan would produce at the same rate, since a shorter term gives the balance less time to accrue interest.
📐 The annual chart, principal-versus-interest bar, and amortization table shown in your results all read from this same fixed payment. Switching repayment frequency doesn’t change the formula, it recalculates the same relationship using a different number of periods per year, though it’s worth noting this means switching frequency alone doesn’t automatically create the “extra payment” acceleration effect some borrowers expect, use the Extra repayments toggle for that.
Assumptions and limitations: the formula is exact given a fixed rate for the entire term, but it assumes the rate never changes, which doesn’t hold once a fixed period ends on a variable-rate loan. Extra repayments, lump sums, and offset balances are all modelled as directly reducing principal in the month they occur, matching how most lenders apply them, but always confirm with your specific lender that extra payments are credited to principal rather than treated as an early instalment of the next regular payment.
Understanding Loan Amortization
Amortization is the process of gradually paying off a loan through scheduled payments over time. Each mortgage payment consists of two components that change in ratio throughout the loan’s life: interest (paid to the lender for using their capital) and principal (which reduces the outstanding loan balance). In the early years of a mortgage, the majority of each payment goes toward interest, a fact that surprises many first-time homebuyers, as the CFPB explains, this is because interest is calculated on the outstanding balance, which is highest at the start of the loan:
| Year | Monthly interest (% of payment) | Monthly principal (% of payment) | Outstanding balance |
|---|---|---|---|
| Year 1 | 80% | 20% | $394,600 |
| Year 5 | 75% | 25% | $369,800 |
| Year 10 | 67% | 33% | $330,200 |
| Year 15 | 56% | 44% | $278,000 |
| Year 20 | 42% | 58% | $209,300 |
| Year 25 | 24% | 76% | $118,900 |
| Year 30 | Near zero | Nearly 100% | $0 |
Example based on $400,000 at 5.5% over 30 years. This front-loading of interest is why early extra repayments have such a powerful impact, every dollar of principal you pay early eliminates decades of interest on that dollar.
How Interest Rate Affects Your Mortgage
Interest rate is the most influential variable in mortgage cost. Even 0.5% makes a dramatic difference over a 30-year term:
| Interest rate | Monthly payment ($400K, 30yr) | Total interest paid | Total loan cost |
|---|---|---|---|
| 4.0% | $1,910 | $287,000 | $687,000 |
| 4.5% | $2,027 | $329,000 | $729,000 |
| 5.0% | $2,147 | $373,000 | $773,000 |
| 5.5% | $2,271 | $418,000 | $818,000 |
| 6.0% | $2,398 | $464,000 | $864,000 |
| 6.5% | $2,528 | $511,000 | $911,000 |
| 7.0% | $2,661 | $558,000 | $958,000 |
The difference between a 4% and 6% interest rate on a $400,000 mortgage is approximately $177,000 in total interest, nearly half the original loan amount. This is why shopping for the best mortgage rate and considering refinancing when rates fall significantly can save a homeowner more than any other financial decision.
The Power of Extra Repayments
Extra mortgage repayments are one of the most effective wealth-building strategies available to homeowners. Every additional dollar applied to principal today eliminates all future interest charges on that dollar. The mathematics are compelling:
| Extra monthly repayment | Interest saved | Years saved | New payoff date |
|---|---|---|---|
| $0 (standard) | $0 | 0 | 30 years |
| $100/month extra | ~$48,300 | ~2.9 years | 27.1 years |
| $200/month extra | ~$85,700 | ~5.3 years | 24.7 years |
| $500/month extra | ~$161,000 | ~10.3 years | 19.7 years |
| $1,000/month extra | ~$229,600 | ~15 years | 15 years |
Based on $400,000 at 5.5% over 30 years. Use the “Extra repayments” toggle in the calculator above to model your specific scenario. A genuine bi-weekly payment plan, paying half your monthly amount every two weeks (26 payments per year instead of 12 monthly payments), achieves a similar effect by making the equivalent of one extra monthly payment annually. The CFPB notes that borrowers should confirm their loan terms before choosing a bi-weekly payment plan, since some loans carry prepayment penalties, and as explained above, simply switching this calculator’s frequency toggle to bi-weekly recalculates a fresh payment for the same term rather than accelerating payoff.
How to Pay Off Your Mortgage Faster
Switch to bi-weekly repayments
Selecting bi-weekly in this calculator recalculates your payment to still fully amortize over your original term, so the frequency toggle alone won’t shorten your payoff. To model the classic bi-weekly acceleration effect, the equivalent of one extra monthly payment per year, use the “Extra repayments” toggle and add an amount equal to roughly one-twelfth of your monthly payment. Many lenders offer this as a genuine bi-weekly payment plan that automatically achieves the same result.
Round up your repayments
If your repayment is $2,271/month, pay $2,300 or $2,500. The extra $29–229 per month adds up to hundreds of dollars per year in principal reduction that compounds significantly over the loan’s life.
Use an offset account
An offset account links your savings to your mortgage, reducing the interest-bearing balance. $50,000 in an offset account against a $400,000 mortgage means you only pay interest on $350,000. The offset account remains fully accessible, you’re not making extra repayments, just holding savings strategically.
Apply windfalls to principal
Tax refunds, work bonuses, inheritances, or rental income directed to mortgage principal can cut years off the loan term. A $20,000 lump sum in Year 5 of a $400,000 mortgage at 5.5% saves approximately $53,300 in interest over the remaining term.
Refinance when rates drop
If market rates fall more than 1% below your current rate, refinancing your mortgage can save significant amounts. Calculate break-even: divide refinancing costs by monthly savings to find the months needed to recoup costs, typically 18–36 months.
Consider a shorter loan term
A 15-year mortgage vs a 30-year at the same rate saves enormous total interest, typically 55–65% of the 30-year interest cost, while building equity much faster. Monthly payments are higher, but total wealth creation is significantly greater.
3 Real-Life Examples
Three different borrowing situations, calculated the way the tool above does it.
| Situation | Inputs | Result | What it means |
|---|---|---|---|
| First-time buyer with a smaller, shorter loan | $280,000 loan, 6.0% rate, 25-year term, monthly repayments. | Monthly payment: $1,804. Total interest: $261,213. | A smaller loan and shorter term keep the monthly payment more accessible for a first buyer, while still accumulating meaningful interest over the full 25 years. |
| Homeowner using an offset account | $500,000 loan, 5.8% rate, 25-year term, comparing no offset against a $45,000 offset balance. | Without offset: $448,197 total interest. With $45,000 offset: $407,859 total interest. | Holding $45,000 in savings against this mortgage saves approximately $40,300 in interest without the money ever leaving the borrower’s control, the core appeal of an offset account over simply paying down principal. |
| Investor with an interest-only period | $450,000 loan, 6.5% rate, 25-year term, first 3 years (36 months) interest-only. | Interest-only payment: $2,438/month for 3 years. Total interest over the full term: $484,722. | The interest-only period keeps early cash flow lower and builds no equity during those 3 years, after which payments step up to fully amortize the still-full $450,000 balance over the remaining term, exactly the “payment jump” investors need to plan for in advance. |
These are illustrative calculations using the same formula the calculator above applies. They’re a planning tool, not a substitute for an actual loan offer from a lender.
Important Notes
- These are simulated projections, not a loan offer. The EMI formula is exact given a fixed rate and term, but actual approval, rate, and terms depend on your lender and creditworthiness.
- Rounding. Displayed currency figures round to the nearest whole unit, or abbreviate to K, M, or B for large values.
- Switching repayment frequency alone doesn’t accelerate payoff in this calculator. Selecting bi-weekly or weekly recalculates a fresh payment amount targeting the same term, it doesn’t automatically create the “one extra payment per year” effect some borrowers expect from bi-weekly plans. Use the Extra repayments toggle to model that effect directly.
- Interest-only periods build no equity. After the interest-only period ends, the payment recalculates against the still-full principal balance over the remaining term, which typically means a noticeably higher payment than if the loan had amortized from the start.
- Offset and extra-payment features assume funds are applied exactly as modelled. Confirm with your specific lender that offset balances reduce your interest-bearing principal and that extra payments are credited to principal, not treated as an early instalment of the next regular payment.
- This calculator doesn’t include fees, closing costs, or rate changes over time. Origination fees, valuation fees, and any future rate resets on a variable loan aren’t reflected in the figures shown.
- Data privacy. All calculations run in your browser. Your inputs aren’t sent to a server, and the PDF is generated locally on your device.
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