Down payment comparison calculator

Compare cash today with payment pressure later

A larger down payment normally reduces the loan balance and may remove private mortgage insurance, but it also consumes more cash at closing. This calculator places those consequences side by side instead of forcing a choice on gut feeling.

Who should use this calculator

Use it when you have flexibility in how much to put down and want to see the actual monthly and cash trade-off, not just the general idea that "more down means less PMI." It is especially useful when a smaller down payment would leave too little cash for closing, moving, and a reserve — a risk this comparison makes visible before you commit.

What each input means

• Purchase price, mortgage rate, and loan term — shared by both scenarios so only the down payment and PMI change.
• Closing costs — added to each scenario's down payment to show total cash needed.
• Scenario A and B down payment and PMI — the two down-payment percentages being compared, each with its own user-entered annual PMI rate (enter 0 where PMI would not apply, typically at or above 20% down).

How the calculation works

For each scenario, the calculator computes the down payment, loan amount, fixed-rate principal and interest, and PMI (loan amount times the entered annual PMI rate). Cash needed is the down payment plus closing costs; monthly cost is principal and interest plus PMI.

A worked example, using the figures already loaded above

On the default $450,000 purchase, Scenario A (5% down, 0.7% PMI) requires $34,500 in cash (down payment plus $12,000 closing costs) and costs about $2,951 a month including PMI. Scenario B (20% down, no PMI) requires $102,000 in cash and costs about $2,275 a month. Putting 20% down instead of 5% costs an extra $67,500 in cash up front, in exchange for a payment that is about $676 a month lower.

How to interpret the result

Divide the extra cash required by the monthly savings to see roughly how many months it takes the lower payment to "earn back" the extra down payment — in the example above, about 100 months, ignoring what that cash could otherwise earn. The right choice depends on what else that cash could do for you and how much monthly payment room you actually have, not on which payment is lower in isolation.

What is deliberately separate

• Property taxes, homeowners insurance, HOA dues, and maintenance are not included here.
• The two scenarios use the same interest rate unless you replace it with separate lender quotes.
• PMI is a user-entered planning rate, not an insurer or lender quote.

Why the result is an estimate

Both scenarios use the same simplified fixed-rate math on numbers you supplied. A real lender may price a lower down payment at a different rate than a higher one, and actual PMI rates depend on credit profile and loan program — neither is modeled here.

Common mistakes to avoid

• Choosing the larger down payment without checking whether enough cash remains for closing, moving, immediate repairs, and an emergency reserve.
• Assuming the interest rate is identical across down-payment tiers — ask your lender whether it actually is.
• Forgetting that PMI is usually temporary (see the PMI Timeline Estimator), which changes the true cost of the smaller down payment over time.

Related guides and calculators

• Cash to Close Calculator — the complete transaction-cash plan for either scenario.
• True Monthly Home Cost calculator — recurring ownership costs this comparison leaves out.
• PMI Timeline Estimator — see roughly how long PMI would last on the lower-down-payment scenario.
• What closing costs mean for your cash — how the down payment fits into the full cash-to-close equation.