How it works
A down payment timeline is the projected month your house fund reaches the required cash for a purchase — solved here as a genuine race, because both sides move. Your fund compounds monthly from its current balance plus every deposit at the account's APY, while the cash requirement itself inflates: the target price appreciates at its own annual rate, so the 20% you must produce grows even as you save. The calculator advances both month by month until the fund crosses the requirement, then reports the date, the grown purchase price, and exactly how much of the added burden came from appreciation rather than your original math. On defaults, a $425,000 home appreciating 3% demands about $100,200 down by the time a $28,000 start plus $900 a month catches it five and a half years out — roughly $15,200 more than today's $85,000 figure, partially offset by the $13,800 of interest earned en route. That asymmetry is the strategic point: savings yield around 4%, but the target compounds too, so buying sooner at a lower price often beats saving longer for a bigger slice of a pricier house. The schedule table shows the gap closing (or stalling) year by year, which is the honest way to test whether your pace survives a moving market.
Formula
Fund(m) = saved·(1+r)^m + pmt·((1+r)^m − 1)/r | Required(m) = price × DP% × (1+h)^m | timeline = first m where Fund(m) ≥ Required(m), r = APY/12, h = appreciation/12
Tips
- Compare timelines at 0% appreciation too — the difference shows what waiting for a bigger fund really costs.
- PMI on 5–10% down often costs less than three extra years of rent plus appreciation; price both paths.
- Keep the fund in a high-yield account, never stocks — horizons under five years cannot absorb a downturn.
- Re-run after every raise: contributions move the date far more than rate-hunting does.
- If the gap stalls, check the appreciation assumption against local data rather than national averages.
Frequently asked questions
- How long does it take to save a 20% down payment?
- On this calculator's defaults — a $425,000 home, $28,000 already saved and $900 a month earning 4% — about 5 years and 6 months, arriving near a $100,200 requirement once 3% appreciation works against you. Faster contributions compress it dramatically: $1,400 a month cuts the wait to roughly three and a half years.
- Should I save for 20% down or buy with 5%?
- Run both timelines. Five percent on the same home starts near $21,250 — a threshold this default profile's savings already clear — but adds PMI of roughly 0.5–1.5% of the loan per year until you reach 20% equity. Three extra years of saving can cost more in appreciation and rent than several years of PMI would.
- How much does home-price appreciation affect my down payment?
- Directly and multiplicatively. At 3%, the 20% requirement on this default home climbs from $85,000 to about $100,200 over five and a half years — roughly $15,200 of extra cash needed purely from price growth, only partly offset by the roughly $13,800 your fund earns in interest along the way.
- Where should I keep my house down payment fund?
- A high-yield savings account, money market fund, or short CDs and Treasuries laddered to your likely purchase window — principal-safe and liquid. Investing it in stocks risks arriving exactly when markets fall, which historically delays purchases by years, not months. Keep it boring on purpose.
- Does it make sense to wait for a bigger down payment?
- Only if the timeline math says so. Every extra year adds appreciation to the entry price while your 4% yield barely dents the growing requirement. The schedule's gap column makes the trade-off visible: if the gap barely shrinks year to year, waiting is running in place.