Mortgage Calculator
Estimate your monthly mortgage payment, including principal & interest, property tax, and homeowners insurance.
Monthly Payment
$0
- Principal & Interest $0
- Property Tax $0
- Insurance $0
- Total Monthly Cost $0
Loan amount: $0
Educational estimate only. The live result above is a planning number, not a pre-approval, Loan Estimate, or offer. Tax and insurance in the form are annual amounts you type; they are not an assessment from any county.
Who this is for
Use this page when you are comparing a purchase price, down payment, rate, or term and want a transparent monthly housing draft. The decision it helps is “what does this loan cost each month, and how much of that is interest versus tax and insurance?” It is for US-style fixed-rate, fully amortizing home loans. It is not a cash-offer worksheet, an ARM payment-shock model, or a refinance cash-out engine.
How this mortgage calculator works
Principal and interest use the standard amortizing installment formula:
M = P · [r(1+r)n] / [(1+r)n − 1]
- P — loan principal (home price minus down payment)
- r — monthly interest rate (annual rate ÷ 12)
- n — total number of monthly payments (years × 12)
If the annual rate is 0%, the formula is unnecessary: M is P / n. Property tax and homeowners insurance are divided by 12 and added to P&I to estimate PITI (principal, interest, taxes, insurance). Those extras do not reduce the loan balance.
The formula assumes a fixed rate, monthly payments that match monthly compounding, and no extra principal. It is the same relation used for many installment loans and the same helper (`calcAmortizedLoan`) that powers the auto-loan page. For a consumer-facing explanation of how lenders build a level P&I payment, see the CFPB’s Ask CFPB note How do mortgage lenders calculate monthly payments?.
Worked example (visible without JavaScript)
These figures match the form defaults: a $400,000 home, 20% down, 6.5% annual rate, 30 years, $5,000 property tax, and $1,500 insurance. You can check them with a basic calculator. JavaScript is only needed if you want to change the inputs.
Principal P = $400,000 − $80,000 = $320,000. Monthly rate r = 0.065 / 12 ≈ 0.00541667. Term n = 360. Then (1 + r)360 ≈ 6.97347, so:
- Numerator: 320,000 × 0.00541667 × 6.97347 ≈ 12,088.68
- Denominator: 6.97347 − 1 ≈ 5.97347
- Monthly P&I: 12,088.68 / 5.97347 = $2,022.62
| Item | Amount |
|---|---|
| Home price | $400,000 |
| Down payment (20%) | $80,000 |
| Loan principal | $320,000 |
| Monthly P&I | $2,022.62 |
| Property tax ($5,000 / 12) | $416.67 |
| Homeowners insurance ($1,500 / 12) | $125.00 |
| Estimated PITI | $2,564.28 |
Month 1 interest is $320,000 × 0.065 / 12 = $1,733.33. Principal in that payment is $2,022.62 − $1,733.33 = $289.28. Over 360 payments, P&I totals about $728,142, of which about $408,142 is interest if you never pay extra and never refinance.
Same house, 10% down, plus illustrative PMI
If the down payment is $40,000, principal becomes $360,000. The same 6.5% / 30-year formula produces P&I of $2,275.44. Tax and insurance are unchanged ($541.67 combined), so PITI is $2,817.11. Many conventional loans at 90% loan-to-value also add PMI. This tool does not compute PMI. An illustrative 0.50% of $360,000 is $1,800 / year, or $150 / month — a planning add-on, not a quoted premium.
| Item | Amount |
|---|---|
| Loan principal | $360,000 |
| Monthly P&I | $2,275.44 |
| Tax + insurance | $541.67 |
| PITI (what this tool reports) | $2,817.11 |
| Illustrative PMI (0.50% / yr) | $150.00 |
| Planning total with PMI | $2,967.11 |
Lifetime interest on that $360,000 loan is about $459,160 — roughly $51,000 more than the 20% down case — before counting PMI premiums. PMI rates are set by the insurer and the loan file; 0.50% is only a worked example so the fifth line is visible.
Show the math
r (monthly rate) = 6.5% ÷ 12 = 0.5417%
n (months) = 30 × 12 = 360
M = P · [r(1+r)n] / [(1+r)n − 1] = $2022.62
+ tax/12 = $416.67 + insurance/12 = $125.00
Total monthly = $2564.28
Assumptions and limitations
- Fixed rate, fully amortizing, monthly payments. Adjustable-rate mortgages, interest-only periods, balloons, and biweekly products need a different schedule.
- No PMI, mortgage insurance premium, or FHA/VA funding fee in the live total.
- No HOA dues, flood insurance, earthquake insurance, or homeowners-association special assessments.
- No discount points, origination fees, prepaid interest, or other closing costs. Those change cash-to-close, not the amortizing P&I formula.
- Property tax and insurance are annual totals ÷ 12. Real escrow accounts true-up when the tax bill or premium changes.
- No extra principal payments, recasts, or refinances.
- The rate you type is the note rate used for amortization, not a complete APR.
Sources and data vintage
Payment equation: standard fully amortizing installment formula M = P r (1 + r)n / ((1 + r)n − 1), with r as the monthly periodic rate. Consumer-facing discussion: CFPB, “How do mortgage lenders calculate monthly payments?” and “How does paying down a mortgage work?” (Ask CFPB). We do not treat the formula as a statute.
The numeric example uses the calculator’s shipped defaults so a hand check and the live form can match. Tax and insurance amounts are illustrative annual inputs, not a 2026 county levy. Example reviewed for this page: 2026-09-16.
Frequently asked questions
What is the formula for monthly mortgage payments?
The standard fully amortizing formula is M = P · [r(1+r)^n] / [(1+r)^n − 1], where P is the loan principal (home price minus down payment), r is the monthly interest rate (annual rate ÷ 12), and n is the number of monthly payments (years × 12). If the rate is 0%, M is simply P / n. This is ordinary installment-loan math, not a mortgage-only statute. The Consumer Financial Protection Bureau describes the same level principal-and-interest payment for a fixed-rate, fully amortizing loan.
How much should I put down on a house?
Conventional loans often allow 5–20% down. Many lenders require private mortgage insurance (PMI) below 20% down. FHA loans can allow 3.5% down for eligible borrowers, but FHA mortgage insurance is a different product and is not computed here. This calculator’s default is 20% on a $400,000 home — $80,000 — which leaves a $320,000 principal and typically avoids PMI on a conventional loan.
What is included in PITI?
PITI is Principal, Interest, Taxes, and Insurance. On the default scenario, monthly P&I is $2,022.62, property tax is $5,000 / 12 = $416.67, and homeowners insurance is $1,500 / 12 = $125.00, for a $2,564.28 housing draft. PMI, if any, is a fifth line. This tool adds tax and insurance as simple annual totals ÷ 12; it does not escrow, true-up, or compute PMI.
Does this calculator include PMI?
No. PMI is not an input and is not in the monthly total. Lenders set PMI from credit score, loan-to-value, and product type; a common planning range is roughly 0.3%–1.5% of the original loan per year, but that is not a statutory rate. On a $400,000 home with 10% down ($360,000 loan), an illustrative 0.50% PMI is $1,800 / year or $150 / month. Add that to the $2,817.11 PITI from this tool and the planning total is about $2,967.11.
How does a 15-year term compare with 30 years?
On the $320,000 default loan at 6.5%, 30-year P&I is $2,022.62 and lifetime interest is about $408,142. The same principal and rate over 15 years raises P&I to $2,787.54 and cuts lifetime interest to about $181,758. The monthly payment rises by about $765; the interest column falls by roughly $226,000 if you never refinance or pay extra.
What's the difference between the mortgage rate and APR?
The note rate is what the amortization formula uses. APR folds in certain lender fees (origination, points, some prepaid finance charges) and is usually higher. This calculator uses the interest rate you type, not a Regulation Z APR disclosure. Discount points are not modeled: paying 1 point is typically 1% of the loan at closing in exchange for a lower note rate, and that cash is outside the monthly formula.
Are HOA dues, flood insurance, or closing costs included?
No. HOA or condo dues, flood insurance, earthquake insurance, title insurance, origination fees, discount points, prepaid interest, and cash-to-close are out of scope. Those items can be large and they do not amortize with the loan. A lender’s Loan Estimate is the document that itemizes them.
How much of the first payment is interest?
Interest for a month is remaining balance × monthly rate. On the $320,000 / 6.5% default, month 1 interest is $320,000 × 0.065 / 12 = $1,733.33. The rest of the $2,022.62 P&I is principal: $289.28. After that payment the balance is $319,710.72. Early payments are interest-heavy because the unpaid balance is largest at the start.
What happens if I pay extra principal?
An extra principal payment reduces the balance immediately, so every later interest charge is computed on a smaller number. This page assumes a level schedule with no extra payments, no recast, and no refinance. If you pay extra, the remaining term shrinks or the last payment shrinks; the advertised monthly P&I does not automatically drop unless the loan is recast.
Can I treat this monthly total as a lender quote?
No. This is an educational estimate for comparing price, down payment, rate, and term. A real payment can also include PMI, HOA, flood coverage, lender-required escrow cushions, and fees that never enter this form. Use the formula to understand the shape of P&I; use the official Loan Estimate and Closing Disclosure to decide whether to sign.
Related calculators
- → Auto Loan Calculator — the same amortizing formula on a shorter term and a sales-tax principal.
- → Paycheck Calculator — compare the housing draft with estimated take-home pay.
- → Income Tax Calculator — your federal bracket affects the value of a mortgage-interest deduction if you itemize.
- → Compound Interest Calculator — the opportunity cost of a larger down payment left invested.
- → Guide: how monthly mortgage payments are calculated — a longer walkthrough of the same $400,000 example.
Last reviewed 2026-09-16. Results are educational estimates for planning — not financial, tax, or legal advice, and not a lender quote, payroll stub, or filed return.