Down Payment Calculator

1. Enter the Purchase price ($).
2. Enter a Target down payment (%) greater than 0 and no greater than 100.
3. Enter Current savings ($), or leave it blank to use $0.
4. Choose a future Target purchase date.
5. Optionally enter an Expected annual savings return (%, optional). A blank field uses 0%.
6. Click Calculate to display the plan.

What the calculator shows

After you click Calculate, the result includes the required down payment, months until the target date, required monthly contribution (or On track), and projected savings balance.

It also displays the formula, an assumptions table, and a month-by-month schedule with each contribution, interest or growth amount, and balance. Use Copy result for a plain-text copy or Download result (.txt) to save the same result as a text file.

How the calculation works

The required down payment is the purchase price times the target percentage:

Required down payment = Purchase price x (Target % / 100)

Your current savings are projected forward to the target date at the expected annual return you enter, compounded monthly:

r = Expected annual return / 100 / 12
Projected growth of current savings = Current savings x (1 + r) ^ Months

Whatever is still needed after that growth is the remaining need:

Remaining need = Required down payment - Projected growth of current savings

If the remaining need is 0 or less, your current savings already cover the target and no further monthly contribution is required. Otherwise, the required equal monthly contribution is solved using the future-value annuity formula, so that contributions plus growth reach the required down payment exactly by the target date:

Monthly contribution = Remaining need / [((1 + r) ^ Months - 1) / r]

If the expected return is 0%, this simplifies to dividing the remaining need evenly across the remaining months.

Validation and planning limits

Enter a purchase price greater than 0. The target percentage must be greater than 0 and no greater than 100. Current savings must be 0 or greater, and an entered expected return must be between 0 and 100.

Choose a target purchase date. An empty date, an invalid date, or a date today or earlier produces an error. Any future date is accepted; the calculator rounds the planning period up to whole calendar months. Dates more than 100 years away are rejected.

Assumptions and unit conventions

• Whole calendar months: the planning period is rounded up when the date leaves a partial final month.
• Monthly compounding: any expected annual return is converted to a monthly rate (annual rate / 12) and compounded once per month on the growing savings balance.
• Fixed monthly contribution: the plan assumes the same contribution amount every month for the full period - it does not vary contributions month to month.
• Down payment only: the required amount does not include closing costs, moving costs, taxes, insurance, private mortgage insurance (PMI), or other cash needed at purchase.
• User-supplied return, not a live rate: the expected annual savings return is a planning assumption you choose. It defaults to 0% if left blank and is never fetched from a live account, bank, or market rate.

What is not included

This calculator does not fetch live mortgage rates, savings-account rates, or lender terms, and it does not provide mortgage pre-approval, personalized financial advice, or guarantee any real-world savings outcome. It does not include closing costs, moving costs, taxes, insurance, PMI, or other purchase-related fees beyond the down payment itself. It performs a transparent, fixed-rate savings-plan calculation on the numbers you provide.

Privacy and processing

The calculator values are processed locally by the tool script using the numbers you enter. The page separately includes site analytics and a subscription form.

Frequently Asked Questions