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Down Payment Calculator

Calculate your down payment amount, loan size, and monthly payment for a home purchase.

Last Updated: May 5, 2026
2 min read

Home Details

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Down Payment Needed

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Loan Amount

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Monthly P&I

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A down payment calculator helps homebuyers determine how much they need to save, what loan size they'll qualify for, and how their down payment percentage affects their monthly mortgage payment and Private Mortgage Insurance (PMI) costs.

How to Use This Calculator

  1. Enter the home purchase price.
  2. Enter your down payment amount or percentage (e.g., 20%).
  3. Enter the loan interest rate and term (15 or 30 years).
  4. Click Calculate to see loan amount, monthly payment, and PMI cost if applicable.

What This Calculator Measures

  • Down payment amount — The upfront cash you pay at closing (typically 3–20% of purchase price).
  • Loan amount — Purchase price minus down payment; the amount you borrow.
  • Monthly mortgage payment — Principal + interest based on the loan amount, rate, and term.
  • PMI cost — Private Mortgage Insurance required when down payment is less than 20% (typically 0.5–1.5% of loan value annually).

Formula or Logic

Loan Amount = Purchase Price − Down Payment

Monthly Payment = Loan Amount × [r(1+r)^n] ÷ [(1+r)^n − 1]

PMI (monthly) ≈ (Loan Amount × PMI Rate) ÷ 12 — required until LTV drops below 80%.

Example Calculations

Example 1: $400,000 home, 10% down ($40,000) → Loan = $360,000. At 6.5% for 30 years → Payment = $2,275/month + ~$150 PMI. At 20% down ($80,000) → Payment = $2,023/month, no PMI.

Example 2: $250,000 home, 3.5% FHA down ($8,750) → Loan = $241,250. Monthly PI = $1,526. PMI/MIP adds ~$176/month.

Understanding Your Results

A 20% down payment eliminates PMI and reduces your loan balance significantly. However, a smaller down payment lets you enter the market sooner and keep cash for renovations or investments. Calculate the breakeven between paying PMI vs. investing the withheld down payment.

Common Mistakes to Avoid

  • Forgetting that the down payment is not your only upfront cost — closing costs add 2–5% of the purchase price.
  • Putting all savings into the down payment and having no emergency fund.
  • Not comparing FHA loans (3.5% down) vs. conventional loans with PMI for low-down-payment scenarios.
  • Underestimating PMI duration — it may take years to reach 80% LTV at a low down payment.