Down Payment Calculator

What this calculator does

This down payment calculator answers a single question: how long until you have the cash. Enter your target home price, the percentage you want to put down, how much you can save each month, and the mortgage rate you expect, and it returns the dollar amount you need and the number of months and years of saving that gets you there.

The table underneath is what makes it useful. Year by year it shows how much you have saved, what percentage of the home price that represents, and the monthly mortgage payment you would end up with if you stopped saving and bought at that point — so you can see what buying earlier with less down actually costs.

When to use it

Use it when you have a price range in mind and want a date rather than a vague sense of someday. It converts a savings rate into a timeline, which is what makes the goal manageable.

It is also the tool for the impatience question. If 20 percent takes four and a half years but ten percent takes just over two, compare the two years of continued rent and rising prices against a couple of years of PMI. Run it again whenever your savings rate changes — a raise, a partner moving in, or clearing a car loan can pull a distant target forward by a year or more.

Understanding the inputs

Target home price should be a real price from listings you would actually bid on, not a round number. Target down payment is the percentage; the meaningful values are three and 3.5 percent for the minimums, five and ten percent for common middle ground, and 20 percent for the PMI threshold.

Monthly savings should be what you can genuinely set aside after rent and existing debt, and it should be net of the emergency fund you keep separate — do not plan to arrive at closing with zero reserves, since lenders like to see a couple of months of payments left over. The interest rate input drives the resulting payment column, so use a rate you have been quoted rather than a national average.

How is this calculated?

Down Payment = Property Price × (Down Payment %) / 100. Months to Goal = (Down Payment − Current Savings) / Monthly Savings.

A worked example

Say you are targeting a $400,000 home with 20 percent down and can save $1,500 a month. The goal is $80,000, which takes 54 months — four and a half years of saving with nothing else going wrong.

Now test ten percent instead. The goal drops to $40,000 and the timeline to 27 months, just over two years. The cost is a $360,000 loan rather than $320,000: at 6.5 percent that is about $2,275 a month instead of $2,022, plus roughly $180 a month of PMI until you reach 20 percent equity. So buying two and a half years earlier costs around $433 more per month, with the PMI portion falling away in a few years.

Limitations and assumptions

The model assumes your savings earn nothing, your income is steady, and the target price never moves. In a market appreciating four percent a year, the last of those is the one that hurts — your goal grows while you chase it, which is exactly why long timelines to 20 percent often lose to shorter ones with PMI.

It also excludes closing costs entirely, which is the biggest practical gap: two to five percent of the price has to come from somewhere, alongside prepaid escrow for taxes and insurance and any moving expenses. And it does not model gift funds, down payment assistance, or an IRA withdrawal. Once you have a target date, ask a lender for a full cash-to-close estimate rather than budgeting for the down payment alone.