Mortgage Calculator
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Calculate your exact monthly mortgage payment — principal and interest, PMI, property tax — with a full amortization breakdown.
🏡 Mortgage Calculator
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How to Use the Mortgage Calculator
Enter the home price and down payment
Input the purchase price and your down payment amount. Down payment below 20% triggers PMI — the calculator factors this into your total monthly cost.
Set the interest rate and term
Enter the rate from your lender's quote — not an estimate. Even 0.25% changes the total interest paid by thousands. Choose 15 or 30-year term; the difference in total interest is often $150,000–$250,000.
Add tax, insurance, and HOA
Input annual property tax, homeowner's insurance, and any HOA fees. These bring the payment from principal-and-interest to the true PITI (principal, interest, tax, insurance) — the figure your lender uses for DTI qualification.
Review the amortization schedule
Check how much of your early payments go toward interest vs principal. In year one of a 30-year mortgage, often 80–85% of each payment is interest — the schedule makes this visible and shows the payoff acceleration from extra payments.
How Mortgage Payments Are Calculated
Mortgage payments consist of principal (paying back the loan), interest (cost of borrowing), and often escrow payments for property tax and insurance. The principal and interest portion is calculated using the standard loan amortization formula.
📐 Mortgage Payment Formula
r = 7.5% / 12 = 0.00625; n = 360
M = $320,000 × [0.00625 × (1.00625)³⁶⁰] ÷ [(1.00625)³⁶⁰ − 1]
M = $320,000 × 0.007392 = $2,236/month
Amortization — Why You Pay Mostly Interest Early
In the early years of a mortgage, the vast majority of each payment goes to interest, not principal. For a $400,000 30-year mortgage at 7.5%, your first payment of ~$2,797 includes about $2,500 in interest and only $297 in principal. By year 15, the split approaches 50/50. This is why extra principal payments early in the loan save substantial interest.
How is a Monthly Mortgage Payment Calculated?
Your monthly mortgage payment has two core components: principal and interest (P&I), plus optional escrow payments for property tax and homeowner's insurance. The P&I portion is calculated using the standard amortization formula, which ensures the loan is fully paid off by the end of the term through fixed equal payments.
The formula is: M = P × [r(1+r)^n] / [(1+r)^n − 1] where M is monthly payment, P is loan amount, r is monthly interest rate (annual ÷ 12), and n is number of payments (years × 12).
How to Calculate Your Mortgage Payment Manually
Calculate the monthly interest rate
Divide your annual interest rate by 12. For a 7% annual rate: 7 ÷ 12 = 0.5833% = 0.005833 monthly rate.
Calculate the number of payments
Multiply loan years by 12. A 30-year mortgage = 360 payments. A 15-year = 180 payments.
Apply the amortization formula
For a $320,000 loan at 7%, 30 years: M = $320,000 × (0.005833 × 1.005833^360) / (1.005833^360 − 1) = $2,129/month.
Add tax and insurance
Add monthly property tax (annual tax ÷ 12) and monthly insurance (annual insurance ÷ 12) to get your total PITI payment.
Mortgage Rates in 2025 — What to Expect
Mortgage rates fluctuate based on Federal Reserve policy, inflation, and bond markets. After a period of elevated rates in 2023–2024, rates have begun to moderate. Always compare at least 3 lenders — even a 0.25% rate difference on a $300,000 mortgage saves over $15,000 in total interest over 30 years.
Financing property in South Africa? South African home loans are called bonds — and unlike US mortgages, SA bond repayments are calculated on a variable prime-linked interest rate set by the South African Reserve Bank. Upfront costs also include transfer duty, conveyancing attorney fees, and bond registration charges. If you're looking to invest in property in South Africa, SA Property Tools provides SA-specific bond repayment calculators, transfer duty estimates, and a full suite of South African property tools.
15-Year vs 30-Year Mortgage — Which Saves More?
| Feature | 15-Year Mortgage | 30-Year Mortgage |
|---|---|---|
| Monthly payment | Higher (~40% more) | Lower |
| Total interest paid | Much less (often 50% less) | More |
| Interest rate | Typically 0.5–0.75% lower | Higher |
| Best for | Those who can afford higher payments | Cash flow flexibility |
What is PMI and When Do I Need It?
Private Mortgage Insurance (PMI) is required when your down payment is less than 20% of the home's purchase price. PMI typically costs 0.5–1.5% of the loan amount annually. On a $400,000 loan, that's $2,000–$6,000 per year ($167–$500/month). PMI protects the lender, not you — once you reach 20% equity, you can request its removal.
How Much Mortgage Can I Afford?
The standard guideline is the 28/36 rule: housing costs should not exceed 28% of gross monthly income, and total debt payments should not exceed 36%. For a $90,000 annual salary ($7,500/month), this means a maximum housing payment of $2,100/month. Use our Home Affordability Calculator for a precise figure.
How Extra Principal Payments Change a Mortgage: A Second Worked Example
Beyond the standard $300,000-at-6%-for-30-years example above, consider what happens when you add $200 extra to principal every month. The unmodified payment is $1,798.65 with $347,515 of total interest over 30 years. Simulating the balance with the extra $200 applied monthly, the loan pays off in roughly 23 years and 4 months instead of 30 — nearly 7 years early — and total interest drops to approximately $262,000, a saving of roughly $85,000 for committing an extra $200 a month.
Why is an extra payment early in the loan worth more than the same extra payment made later?
Every dollar applied to principal today stops accruing interest for every remaining month of the loan — a $200 extra payment in month 1 saves interest across all 359 remaining months; the identical $200 paid in month 300 only saves interest for 60 remaining months. This is why even modest, consistent extra payments made from the start of a mortgage produce outsized interest savings compared with the same total extra dollars paid later or in a lump sum near the end.
Should You Choose a Fixed or Adjustable-Rate Mortgage?
What is the practical trade-off between a 30-year fixed and an ARM?
A fixed-rate mortgage locks the same rate — and the same $1,798.65 payment in the example above — for the full term, regardless of what happens to interest rates afterward. An adjustable-rate mortgage (ARM) typically offers a lower introductory rate for a fixed period (commonly 5, 7, or 10 years) before adjusting periodically based on a benchmark index. ARMs can make sense for buyers confident they'll sell or refinance before the adjustment period ends; they carry real payment-uncertainty risk for anyone planning to stay long-term.
How much does a half-point rate difference actually matter?
On the $300,000, 30-year example, moving from 6% to 6.5% raises the monthly payment from $1,798.65 to roughly $1,896.20 — about $97.55 more per month, or roughly $35,000 more in interest over the full term. Rate shopping across three or more lenders, which typically costs nothing but a bit of time, routinely surfaces differences of a quarter to half a percentage point, making it one of the highest-value steps in the entire home-buying process.
When does refinancing this mortgage make sense?
Refinancing generally pays off when the new rate is enough lower than the current one that the monthly savings recoup the closing costs (typically 2–5% of the loan amount) within a timeframe shorter than how long you plan to keep the loan. On a $300,000 balance, refinancing costs of roughly $7,500 recouped by a $150/month payment reduction would take 50 months (about 4 years) to break even — a refinance only makes sense if you're confident you'll hold the loan well beyond that point.
Frequently Asked Questions
Sources & Methodology
Calculations are based on the most current publicly available data from authoritative government and industry sources: