Mortgage Calculator
Calculate your monthly mortgage payment, total interest, and complete amortization schedule. Includes 15 vs 30-year comparison and extra payment simulator.
| # | Payment | Principal | Interest | Balance |
|---|
How Much Does a Mortgage Really Cost — Total Interest Over 30 Years
The monthly mortgage payment is one of the most consequential financial commitments most Americans make — yet most buyers compare homes based on the monthly payment rather than the total 30-year cost. The average US home in 2026 sells for approximately $400,000 (National Association of Realtors). At a 20% down payment and 6.65% rate, the mortgage is $320,000. The total interest paid over 30 years is $422,272 — more than the original loan amount.
| Loan Amount | Rate (30-yr fixed) | Monthly Payment | Total Interest (30 yr) | Total Paid |
|---|---|---|---|---|
| $200,000 | 6.65% | $1,289 | $263,920 | $463,920 |
| $300,000 | 6.65% | $1,933 | $395,880 | $695,880 |
| $400,000 | 6.65% | $2,578 | $527,840 | $927,840 |
| $300,000 | 7.5% | $2,098 | $455,280 | $755,280 |
| $300,000 | 6.0% | $1,799 | $347,514 | $647,514 |
A 1.5 percentage point difference in rate on a $300,000 mortgage — from 6.0% to 7.5% — costs an additional $107,766 in total interest over 30 years and adds $299/month to the payment. This is why locking the lowest available rate at the time of purchase, and considering refinancing when rates fall, has such a large long-term financial impact.
Should You Choose a 15-Year or 30-Year Mortgage?
Monthly payment: $1,933
Total interest: $395,880
Lower monthly payment gives more cash flow flexibility. Most buyers choose 30-year for affordability. The payment difference can be invested — but requires consistent discipline to capture that benefit.
Monthly payment: $2,532
Total interest: $155,676
Pays off the home in half the time. Builds equity much faster. Interest rate is typically 0.5–0.75% lower than 30-year. Saves $240,204 in total interest versus the 30-year option.
The practical question is not which is mathematically better — the 15-year always wins on total cost. The question is whether the higher payment leaves adequate cash flow for emergencies, retirement contributions, and life expenses. Most financial advisors recommend prioritising 401(k) employer match and emergency fund before opting for the 15-year payment premium.
Current Mortgage Rates in 2026 and How They Affect Your Payment
| Rate Change | Effect on $300K Monthly Payment | Effect on 30-yr Total Interest |
|---|---|---|
| +0.5% (e.g. 6.65% → 7.15%) | +$88/month | +$31,680 |
| +1.0% | +$177/month | +$63,720 |
| −0.5% (refinance trigger) | −$88/month | −$31,680 saved |
| 20% down vs 10% down | −$193/month + no PMI | −$69,480 + PMI savings |
Private Mortgage Insurance (PMI) is required on conventional loans with less than 20% down payment. PMI typically costs 0.5–1.5% of the loan amount annually — on a $320,000 loan, that is $133–$400/month added to the payment until equity reaches 20%. The mortgage calculator does not include PMI automatically — add it manually to get an accurate total monthly housing cost if your down payment is below 20%. Related: use the loan calculator for any fixed-term instalment loan.
Mortgage Calculator — FAQ
Common questions about mortgage payments, rates, and 30-year costs.
On a $300,000 loan (assuming 20% down on a $375,000 home) at 6.65% APR over 30 years: monthly payment is $1,933 for principal and interest. Add property tax (~$250–$500/month), homeowner’s insurance (~$100–$200/month), and PMI if applicable. Total monthly housing cost is typically $2,300–$2,700/month on a $300,000 mortgage in 2026.
At 6.65% on a $300,000 mortgage, total interest over 30 years is $395,880 — more than the original loan amount. At 7.5%, total interest rises to $455,280. At 6.0%, it falls to $347,514. Every dollar of interest rate difference costs approximately $63,000–$75,000 in total interest on a $300,000 loan over 30 years.
The 15-year mortgage is always cheaper in total cost — on a $300,000 loan it saves approximately $240,000 in interest. The 30-year mortgage has a lower monthly payment (~$599/month less on $300K) that preserves cash flow. The right choice depends on whether the higher 15-year payment leaves adequate cash flow for emergencies and retirement savings. Most financial planners recommend maximising employer 401(k) match before opting for the 15-year payment premium.
Extra mortgage payments save significant interest by reducing the principal faster. On a $300,000 mortgage at 6.65%: adding $200/month saves approximately $68,000 in total interest and pays off the loan 5 years early. Adding one extra full payment per year saves approximately $82,000 and pays off 6 years early. The mortgage calculator’s extra payment simulator shows exact savings for any additional amount.
Minimum credit score requirements in 2026: Conventional loan: 620 minimum (680+ for best rates). FHA loan: 580 with 3.5% down, 500 with 10% down. VA loan: no official minimum but lenders typically require 620+. USDA loan: 640 minimum. Higher credit scores qualify for lower rates — the difference between 680 and 760 on a $300K mortgage can be 0.5–1% in rate, saving $30,000–$65,000 in total interest.
PMI (Private Mortgage Insurance) is required on conventional loans with less than 20% down. It protects the lender — not you — if you default. Cost: typically 0.5–1.5% of loan amount annually, or $133–$400/month on a $320,000 loan. Under the Homeowners Protection Act, you can request PMI cancellation when your equity reaches 20% of the original purchase price. Lenders must automatically cancel it when equity reaches 22%.
The standard rule is that total housing costs (mortgage, tax, insurance, PMI) should not exceed 28% of gross monthly income, and total debt payments should not exceed 36–43%. On a $80,000 annual salary ($6,667/month gross): maximum housing payment is approximately $1,867/month. At 6.65% with 20% down, that payment supports a home purchase price of approximately $280,000–$300,000. Use the mortgage calculator above to model specific scenarios.