Down Payment Calculator
How long it takes to save a deposit, what it has to be, and how much mortgage insurance a small deposit costs.
The deposit is the part of a purchase you pay from your own money, and its size decides both the mortgage you need and the rate you are offered. Below a fifth of the price, many lenders add mortgage insurance, which is a real monthly cost rather than a one-off fee.
Enter the price, the deposit share you are aiming for, what you have saved and what you can add each month, and this calculator gives the target, the timeline and the effect of a smaller deposit.
At a glance
- What you enter
- Home price, Target deposit share, Already saved for the deposit, Monthly saving, Annual interest on the savings, Alternative smaller deposit share, Mortgage insurance rate
- What you get
- Deposit you need, Months until you have it, Still to save, Mortgage insurance per month with a smaller deposit, That insurance over five years
- Formula shown
- Yes - every step, right below your results.
- Cost and privacy
- Free, no account needed, and nothing you type is stored.
See worked examples ↓ Read the FAQ ↓ Share this calculator ↓
Results are estimates for general information only - always verify with a professional or official source before acting on them.
How to use the Down Payment Calculator
- 1 Enter Home price
- 2 Enter Target deposit share - A fifth is the point where many lenders stop charging mortgage insurance.
- 3 Enter Already saved for the deposit
- 4 Enter Monthly saving
- 5 Enter Annual interest on the savings
- 6 Enter Alternative smaller deposit share - Compare what a smaller deposit would cost you.
- 7 Enter Mortgage insurance rate - Per year on the loan amount. Check your lender or insurer for the real figure.
- 8 Press Calculate. You get Deposit you need, Months until you have it, Still to save, Mortgage insurance per month with a smaller deposit, That insurance over five years, and every intermediate step stays visible under “How is this calculated?”
- 9 Change one number at a time to see what moves the result - that is usually the most useful thing a calculator can tell you.
Worked examples
Real numbers run through this calculator. Open any example to load it into the form above and change it.
A 20% deposit on $400,000 with interest on the savings
A household saving $1,200 a month towards an $80,000 deposit at 4% while it saves.
You enter
- Home price
- $400,000.00
- Target deposit share
- 20%
- Already saved for the deposit
- $25,000.00
- Monthly saving
- $1,200.00
- Annual interest on the savings
- 4%
- Alternative smaller deposit share
- 10%
- Mortgage insurance rate
- 0.60%
You get
- Deposit you need
- $80,000.00
- Months until you have it
- 40
- Still to save
- $55,000.00
- Mortgage insurance per month with a smaller deposit
- $180.00
- That insurance over five years
- $10,800.00
The target is $80,000 and you have $25,000, so $55,000 is still to find. At $1,200 a month with 4% interest it takes about 40 months, during which you deposit $48,151 of your own money and the interest adds $6,849. Dropping to a 10% deposit would leave a $360,000 loan and cost about $180.00 a month in mortgage insurance, which is $10,800 over five years.
A 10% deposit on $250,000 with no interest on the savings
A saver keeping the money in a current account and comparing a 5% deposit.
You enter
- Home price
- $250,000.00
- Target deposit share
- 10%
- Already saved for the deposit
- $8,000.00
- Monthly saving
- $700.00
- Annual interest on the savings
- 0%
- Alternative smaller deposit share
- 5%
- Mortgage insurance rate
- 0.80%
You get
- Deposit you need
- $25,000.00
- Months until you have it
- 24
- Still to save
- $17,000.00
- Mortgage insurance per month with a smaller deposit
- $158.33
- That insurance over five years
- $9,500.00
The target is $25,000 and you have $8,000, so $17,000 is still to find. At $700 a month with no interest that is a little over two years, and every dollar of the deposit comes from you. A 5% deposit would leave a $237,500 loan and cost about $158.33 a month in mortgage insurance at 0.8%, which is $9,500 over five years: the shorter wait is bought with a larger loan and a permanent monthly charge.
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Frequently asked questions
Is the target deposit a percentage or an amount?
You enter the share as a percentage and the calculator turns it into an amount: the price multiplied by the share. On a $400,000 home a 20% target is $80,000. The gap is that target minus what you have already saved, and the months line divides the gap by your monthly saving once interest is allowed for.
If you would rather work from a fixed amount, divide it by the price to get the share to enter. A deposit of $50,000 on a $400,000 home is a share of 12.5%.
How does interest on the savings change the timeline?
With a rate of zero the months are simply the gap divided by the monthly deposit. With interest, each month the balance earns a little and the monthly deposit compounds with it, so the target arrives sooner. The calculator solves the standard future value formula backwards to find the number of months.
The interest earned line shows how much of the deposit the bank paid for rather than you. It assumes the rate stays the same for the whole period and that every deposit arrives on time, which is optimistic for a variable savings rate but useful for showing the size of the effect.
What does a smaller deposit really cost?
Two things. The loan is larger by the difference in the deposit, which raises the repayment, and mortgage insurance is charged on that larger loan. The calculator applies the yearly insurance rate you enter to the smaller-deposit loan, divides by twelve for a monthly figure, and multiplies by five for the five-year cost.
That five-year figure is money that buys you no equity at all. Getting the deposit to the point where insurance stops is usually worth waiting for, especially when the wait is measured in months rather than years.
Are the other costs of buying included in the target?
No. The target is the deposit only. Taxes on the purchase, legal fees, a valuation, a survey, a mortgage arrangement fee and the move itself are paid in cash at completion and are not part of the deposit, so they have to be saved separately or added to your target.
A useful habit is to treat the deposit and the buying costs as two separate pots. The Savings Goal Calculator can hold the second one while this page handles the deposit.
Terms used here
Short, plain-language definitions of the words this calculator uses.