Down Payment Savings Calculator
Quick answer: On a $450,000 home with 20% down, the target is $90,000. With $25,000 saved, $1,500 saved monthly, and 4% APY, the remaining $65,000 gap closes in about 38.5 months — roughly 3 years 3 months. The time comes from n = ln((target·r + PMT) / (savings·r + PMT)) / ln(1 + r), where r is the APY divided by 12 and deposits are assumed at the end of each month.
Working toward a down payment? This down payment savings calculator turns your home price and target percentage into a concrete plan: the dollar amount you need, the gap left to save, how many months it will take, and the date you will finish — all from your current savings, monthly savings, and APY.
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Estimate only. Covers the down payment itself — not closing costs, taxes, fees, or moving expenses. Assumes monthly compounding, constant APY, and end-of-month deposits.
How to use this calculator
Enter the home price you are aiming at and the down payment percentage you want to put down — 20% is the classic benchmark. Add what you have already saved, what you can save each month, and the APY your savings account pays.
The results update instantly: your dollar target, the gap still to save, the months until you get there, and the calendar date you will finish. Try raising the monthly savings to see how much sooner the finish line moves.
How this is calculated
First the target: target = home price × down payment %, and the gap = target − current savings. Then the months n to close the gap come from solving the future-value equation, the same as the savings-goal formula:
n = ln((target·r + PMT) / (savings·r + PMT)) / ln(1 + r), where r = APY ÷ 12.
- If your savings already cover the target, the time is 0 months.
- If APY is 0, the months are simply gap ÷ monthly savings.
- Interest earned is computed over the full (rounded-up) number of months minus total contributions.
Assumptions: monthly compounding, end-of-month deposits, constant APY, no withdrawals, and no closing costs included — the result is an estimate.
Worked example
Inputs: home price $450,000, down payment 20% → target $90,000; current savings $25,000, so the gap is $65,000; monthly savings $1,500; APY 4%.
Monthly rate r = 0.04 ÷ 12 = 0.003333. n = ln((90,000·0.003333 + 1,500) / (25,000·0.003333 + 1,500)) / ln(1.003333) = ln(1,800 / 1,583.33) / ln(1.003333) ≈ 38.5 months, i.e. about 3 years 3 months.
Reference data
This tool is pure math and uses no external data tables. The only constants applied are 12 months per year (to convert APY to the monthly rate) and the 0–100% scale for the down payment percentage. The 20% figure mentioned is a widely cited lending benchmark (it is the down payment level that lets most buyers avoid private mortgage insurance), not a value used in the calculation.
Method & sources
The method is the closed-form solution of the ordinary-annuity future-value equation for the number of periods, applied to a down payment target. All results are computed live in your browser; nothing here relies on external rates or datasets.
- No external data is used; you supply the home price, percentage, and APY. All figures labeled (est.) are estimates from the stated assumptions.
Frequently asked questions
How do I calculate how long it takes to save for a down payment?
First find your target: home price times down payment percentage. Then subtract your current savings to get the gap. With monthly savings PMT and monthly rate r = APY / 12, the months needed are n = ln((target·r + PMT) / (savings·r + PMT)) / ln(1 + r). The calculator above runs this for you and gives a target date.
How much down payment should I save?
Twenty percent is the widely cited benchmark because conventional loans with less than 20% down require private mortgage insurance (PMI) — the cutoff is a loan-to-value ratio above 80% (CFPB/Homeowners Protection Act framework, 2026). Some loan programs allow 3 to 10 percent down. Enter whatever percentage fits your plan — the calculator works with any value from 0 to 100 percent.
Does this include closing costs and moving expenses?
No. It plans savings for the down payment itself only. Closing costs are often another 2 to 5 percent of the home price, plus moving expenses, so consider setting a goal above the pure down payment figure.
Why does the calculator assume a constant APY?
Savings account rates change over time, but a planning calculator needs one number. Enter the rate your savings account currently pays; the result is an estimate, and the time-to-goal barely moves with small rate changes because monthly contributions dominate.
Can I use this for a car or other big purchase?
Yes. Enter any purchase price and any percentage — the math is identical. For a general goal without a percentage, our Savings Goal Calculator is the better fit.