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Buying a home starts with one number: how much cash you will put down on day one. This down payment calculator turns four simple inputs into the figures that actually decide whether a home fits your budget: the down payment amount, the loan amount, the monthly principal-and-interest payment, and the total interest you will pay over the life of the loan. You do not need any finance background to use it. Just follow these steps.
With the default example — a $400,000 home, 20% down, a 6.5% rate, and a 30-year term — the calculator shows a $2,022.62 monthly payment, an $80,000 down payment, a $320,000 loan, and $408,142.36 of total interest. Change only the down payment to 5% and the same inputs produce a $380,000 loan, a payment of about $2,465 per month, and roughly $507,000 of total interest: more than $98,000 extra, before private mortgage insurance is even counted. Running these comparisons takes seconds and can save you five figures, which is exactly why the calculator sits at the top of this page.
A down payment is the lump sum you pay toward the purchase price when you buy a home; the mortgage covers the rest. If you buy a $400,000 house with $80,000 down, you borrow $320,000 and you own $80,000 of the home — your home equity — from the very first day. Lenders express the same idea as the loan-to-value (LTV) ratio: the loan amount divided by the home’s value, times 100. An $80,000 down payment on a $400,000 home means an 80% LTV. The lower your LTV, the less risk the lender takes, which is why bigger down payments earn better interest rates, lower fees, and fewer insurance requirements.
The 20% figure you hear everywhere is a threshold, not a law. Put down 20% or more on a conventional loan and you avoid private mortgage insurance (PMI), a monthly charge that protects the lender — not you — when the down payment is smaller. PMI typically costs 0.3% to 1.5% of the loan amount per year. On a $380,000 loan at 0.85%, that is about $269 added to every monthly payment until you build enough equity to cancel it. Many buyers happily pay PMI for a few years to stop renting sooner; the worked examples below show you exactly what that choice costs in dollars.
How much you must put down depends on the loan program. Conventional loans backed by Fannie Mae and Freddie Mac allow as little as 3% down for qualified first-time buyers. FHA loans, insured by the Federal Housing Administration, require 3.5% down with a credit score of 580 or higher (10% if your score is 500–579). VA loans for eligible veterans and active-duty service members, and USDA loans for qualifying rural buyers, require 0% down. Each program trades a smaller upfront payment for some combination of mortgage insurance, upfront fees, or a slightly higher rate, which is why comparing scenarios in the calculator matters more than chasing any single rule of thumb.
Keep the down payment separate from two other upfront costs. Closing costs — lender origination fees, title insurance, appraisal, prepaid property taxes and homeowners insurance — typically run 2% to 5% of the purchase price and are paid in addition to the down payment. On a $400,000 home, that is $8,000 to $20,000 extra at the closing table. An earnest money deposit, often 1% to 2% of the price, is the good-faith check you write with your offer; it is credited toward your down payment at closing, so it is not an extra cost, just an early one. A realistic cash-to-close plan adds all three together: down payment plus closing costs, minus earnest money already paid, plus the cash reserves some lenders require you to keep.
Finally, remember what the down payment does not do: it does not change the home’s price, and by itself it does not guarantee loan approval. Lenders also weigh your credit score, your debt-to-income ratio, and your employment history. But among the levers you actually control, the down payment is the biggest one — it sets your loan size, your monthly payment, your total interest bill, and whether you pay PMI at all. That is why this page pairs the interactive calculator with the full mathematical breakdown below: so you can see not just the answer, but exactly how it is built.
The calculator runs on three simple formulas. First, the down payment itself:
Down payment = home price × down payment percentage
Loan amount = home price − down payment
LTV ratio = loan amount ÷ home price × 100
The monthly principal-and-interest payment uses the standard amortizing-loan formula, where r is the monthly interest rate (annual rate ÷ 12) and n is the total number of monthly payments:
Monthly payment = loan amount × r(1+r)n ÷ ((1+r)n − 1)
Worked example 1 — 20% down. Take a $400,000 home with 20% down at 6.5% interest for 30 years. Down payment = $400,000 × 0.20 = $80,000. Loan amount = $400,000 − $80,000 = $320,000, so the LTV is 80%. The monthly rate is 0.065 ÷ 12 = 0.00541667 and n = 360 payments. Then (1.00541667)360 ≈ 6.9924. Monthly payment = $320,000 × 0.00541667 × 6.9924 ÷ 5.9924 ≈ $2,022.62. Over 360 payments you pay $2,022.62 × 360 = $728,143.20 in total, of which $728,143.20 − $320,000 = $408,143.20 is interest — the calculator shows $408,142.36, and the few cents of difference are rounding. Because the LTV is exactly 80%, no PMI is due.
Worked example 2 — 5% down. Same $400,000 home, but 5% down at 6.75% for 30 years. Down payment = $400,000 × 0.05 = $20,000. Loan amount = $380,000, so the LTV is 95%. The monthly rate is 0.0675 ÷ 12 = 0.005625, n = 360, and (1.005625)360 ≈ 7.5331. Monthly payment = $380,000 × 0.005625 × 7.5331 ÷ 6.5331 ≈ $2,464.72 of principal and interest. Total interest ≈ $2,464.72 × 360 − $380,000 ≈ $507,299. And because the LTV exceeds 80%, PMI applies: at 0.85% per year, PMI = $380,000 × 0.0085 ÷ 12 ≈ $269.17 per month, pushing the true monthly housing cost to about $2,733.89. Compared with 20% down, this buyer puts $60,000 less down upfront but pays roughly $711 more every single month and about $99,000 more in interest over 30 years. That trade-off — cash today versus cash every month for decades — is the entire down payment decision in one pair of numbers.
Maria is a first-time buyer looking at a $350,000 townhouse. She has $50,000 saved and is deciding between putting 10% down and keeping a cushion, or stretching to 15%. She runs 10% first. Down payment = $350,000 × 0.10 = $35,000. Loan amount = $315,000, LTV = 90%. At 6.625% for 30 years, the monthly rate is 0.06625 ÷ 12 = 0.00552083, n = 360, and (1.00552083)360 ≈ 7.2547. Monthly principal and interest = $315,000 × 0.00552083 × 7.2547 ÷ 6.2547 ≈ $2,017.05.
Because her LTV is above 80%, Maria pays PMI. At 0.6% per year on the $315,000 loan, PMI = $315,000 × 0.006 ÷ 12 = $157.50 per month, so her combined payment is about $2,174.55 before taxes and insurance. Closing costs at 3% add $10,500, so her cash to close is roughly $35,000 + $10,500 = $45,500, leaving her $4,500 of her $50,000 in reserve — thin, but workable, and exactly the kind of insight the calculator-plus-math combination is meant to surface.
She also checks affordability against the classic 28% rule: housing costs should stay under 28% of gross monthly income. $2,174.55 ÷ 0.28 ≈ $7,766 per month, or about $93,200 per year of household income. Finally, she compares 15% down ($52,500, loan $297,500, LTV 85%): the payment drops to about $1,906 in principal and interest plus roughly $141 in PMI, saving about $128 a month — but it would leave her with essentially zero reserves. She chooses 10% and keeps her safety net, a decision she could only make confidently by running the real numbers.
James and Priya want a $525,000 home. They have $60,000 saved — enough for about 11% down plus closing costs — and wonder whether to buy now with 10% down or keep renting for two more years to reach 20%. Assume a 6.25% rate and a 30-year term for both scenarios.
Scenario A — buy now with 10% down. Down payment = $52,500, loan = $472,500, LTV = 90%. Monthly rate = 0.0625 ÷ 12 = 0.00520833, (1.00520833)360 ≈ 6.4886. Monthly principal and interest = $472,500 × 0.00520833 × 6.4886 ÷ 5.4886 ≈ $2,909.59. PMI at 0.55% = $472,500 × 0.0055 ÷ 12 ≈ $216.56 per month, for a combined $3,126.15 per month.
Scenario B — wait and put 20% down. Down payment = $105,000, loan = $420,000, LTV = 80%. Monthly principal and interest = $420,000 × 0.00520833 × 6.4886 ÷ 5.4886 ≈ $2,586.30, with no PMI.
Buying now costs $3,126.15 − $2,586.30 = $539.85 more per month, but waiting requires saving an extra $52,500 while still paying rent. The break-even: $52,500 ÷ $539.85 ≈ 97 months, or about 8.1 years. If they buy now, they can also cancel PMI once the balance hits 80% of the home’s value — through normal amortization that takes roughly 7 to 8 years, and faster if the home appreciates. Total PMI paid in that window would be about $216.56 × 90 ≈ $19,490. Meanwhile, two more years of renting at $2,200 a month costs $52,800 with zero equity built. For James and Priya, buying now with 10% down wins — but only because they did the arithmetic instead of following the “always put 20% down” rule blindly.
1. Draining your emergency fund to hit a bigger down payment. Putting 20% down is not a victory if it leaves you with $500 in the bank when the furnace dies in month two. Keep three to six months of expenses in reserve after closing. On a $350,000 purchase, stretching from 10% to 15% down costs an extra $17,500 — money that cannot also be your safety net.
2. Forgetting closing costs. The down payment is only the largest check, not the only one. At 2% to 5% of the price, closing costs on a $400,000 home add $8,000 to $20,000 on top of the down payment. Buyers who budget exactly 20% and nothing more get an ugly surprise at the closing table. Always budget down payment plus closing costs plus moving expenses.
3. Believing 20% down is mandatory. It is not. FHA loans need just 3.5% ($14,000 on a $400,000 home) and conventional loans go as low as 3% ($12,000). Waiting four years to save 20% while home prices rise 4% annually turns that $400,000 home into a $468,000 home — the “discipline” of waiting can cost more than the PMI you were trying to avoid.
4. Paying PMI forever. PMI is not permanent. On a conventional loan you can request cancellation once your balance reaches 80% of the home’s original value (with a good payment history), and the servicer must drop it automatically at 78%. On the $380,000-loan example above, forgetting to cancel costs $269.17 a month — over $3,200 a year — for coverage that no longer benefits you. Set a calendar reminder tied to your amortization schedule.
5. Confusing the down payment with earnest money, or ignoring rate tiers. Earnest money (1–2% with your offer) is credited toward your down payment — it is not an additional cost. And lenders price by LTV tier: a 95% LTV loan often carries a rate about 0.25% higher than an 80% LTV loan. On a $380,000 balance, that quarter point costs roughly $57 a month, or more than $20,000 over 30 years — a hidden price of the small down payment that the calculator’s rate input lets you model.
Your down payment is one piece of the home-buying puzzle. Use our Mortgage Calculator to model full monthly payments including taxes, insurance, and PMI; the Finance Calculator to plan how much to save each month toward your down payment goal; and the Effective Interest Rate Calculator to compare loan offers whose fees and compounding schedules make headline rates misleading.
Entity: Down Payment Calculator — a mortgage planning tool on Sigma Calculator. Inputs: home price (USD), down payment percentage, annual interest rate (%), loan term (years). Outputs: monthly principal-and-interest payment, down payment amount (USD), loan amount (USD), total interest over the loan term (USD). Core formulas: down payment = price × percent; loan = price − down; LTV = loan ÷ price; monthly payment = P·r(1+r)^n/((1+r)^n−1) with r = annual rate/12, n = years×12. Key thresholds: 20% down avoids PMI on conventional loans (80% LTV); FHA minimum 3.5% down at 580+ credit score; VA and USDA allow 0% down; PMI typically 0.3–1.5% of loan per year, cancellable at 80% LTV on request and automatic at 78% LTV. Reference calculation: $400,000 price, 20% down, 6.5%, 30 years → $80,000 down, $320,000 loan, $2,022.62/month, $408,142.36 total interest.
A 20% down payment on a $400,000 house is $80,000, leaving a $320,000 mortgage. At 6.5% over 30 years, that means about $2,022.62 per month in principal and interest with no PMI. If 20% is out of reach, 10% down is $40,000, 5% is $20,000, and an FHA loan needs just 3.5% ($14,000) — but anything under 20% on a conventional loan adds private mortgage insurance of roughly 0.3% to 1.5% of the loan per year. Budget 2% to 5% of the price for closing costs on top of the down payment.
Yes — every extra dollar down shrinks the loan, and a smaller loan means a smaller payment and less total interest. On a 30-year loan at 6.5%, each additional $10,000 down saves about $63.20 per month and roughly $12,752 in interest over the life of the loan. Crossing the 20% threshold saves even more because it eliminates PMI: on a $380,000 loan at 0.85%, PMI costs about $269 per month until your balance drops to 80% of the home’s value.
On a conventional loan, you can request PMI cancellation once your mortgage balance reaches 80% of the home’s original value — you’ll need a good payment history, and the lender may require a new appraisal ($300–$600). Your servicer must drop PMI automatically when the balance hits 78% of the original value. Making extra principal payments or a lump sum (for example, from a bonus) gets you to 80% faster. Note that FHA loans follow different rules: mortgage insurance lasts 11 years or the life of the loan depending on your down payment.
Sources: Consumer Financial Protection Bureau — “Buying a House” (consumerfinance.gov); Fannie Mae Selling Guide; Freddie Mac Single-Family Seller/Servicer Guide.