Down payment calculator
How much deposit you need for different loan-to-value levels and how long it takes to save.
About the down payment calculator
How much deposit you need for different loan-to-value levels and how long it takes to save.
Part of SmartCalcy’s mortgage & real estate tools. It runs in your browser with no account, uses your own currency and units (change them at the top of the page), and gives estimates for information only, so check official guidance before you rely on a result.
How to use the down payment calculator
What it calculates and when to use it
Find the deposit you need at different percentages of a home’s price and how long it will take to save, using your current savings, monthly saving and interest.
How to use it, step by step
- Enter the home price and the deposit percentage you want.
- Enter what you have saved, how much you can save each month and the interest you earn.
- Read the time to reach the target and the table of common deposit levels.
What each input means
- Deposit you want – A percentage of the price.
- Saved so far – The amount already set aside.
- Monthly saving – How much you add each month.
- Interest on savings – The yearly return you expect.
How to read the results
- Time to save – Months and years until savings reach the target.
- Deposit table – The cash needed and the loan left at 3.5%, 5%, 10%, 15% and 20%.
The formula
Target = price × deposit %. The months n satisfy savings × (1 + i)^n + monthly × ((1 + i)^n − 1) ÷ i = target, where i is the monthly interest rate. The solution is n = ln((target + monthly ÷ i) ÷ (savings + monthly ÷ i)) ÷ ln(1 + i).
A worked example
For a 350,000 home and a 10% deposit the target is 35,000. Starting from 10,000 and saving 800 a month at 4% takes 2 years 5 months.
Assumptions and limits
- Interest compounds monthly and is not taxed.
- Home prices are held flat while you save, but they could rise.
Common mistakes
- Leaving out buying costs on top of the deposit.
- Saving for 20% when a lower deposit with good terms may suit you.
Frequently asked questions
Do I need 20%?
No. In the US a smaller deposit usually means private mortgage insurance. In the UK, rates often improve at 10%, 15% and 25% deposits.
Related tools
Details
- Reach it around
- April 2029
- Loan you would need
- £315,000
- Total you save
- £23,200.00
Deposit at common levels
| Deposit | Amount | Loan |
|---|---|---|
| 3.5% | £12,250 | £337,750 |
| 5% | £17,500 | £332,500 |
| 10% | £35,000 | £315,000 |
| 15% | £52,500 | £297,500 |
| 20% | £70,000 | £280,000 |