House Deposit Calculator

This calculator turns a vague goal — "save for a house" — into two concrete numbers: how much you actually need, and how many months of saving it will take at your current pace. It works backwards from the property price you have in mind and the deposit percentage your lender expects.

It matters because deposit size is the single biggest lever a first-time buyer controls. The jump from a 5% to a 10% deposit, and again from 10% to 15%, typically unlocks meaningfully better mortgage rates — which over a 25-year term compounds into thousands of pounds of interest saved. Working with a clear target also makes it easier to say no to spending that would push the date out.

It's most useful for first-time buyers, anyone returning to the property ladder after a break, and parents helping a child build a deposit. It's less useful once you've actually got a property in mind — by that point a mortgage agreement in principle and the stamp duty figure matter more than a rough savings projection.

A worked example

Aiming at a £280,000 home with a 10% deposit means a target of £28,000. With £6,000 already saved and £500 going in each month, you have £22,000 still to find — roughly 44 months, or just under four years. Stretch to £700 a month and the same target arrives in about 31 months. Drop the deposit target to 15% (£42,000) and at £700/month you'd be looking at a little over four years from today.

Why this matters

A bigger deposit doesn't only mean a smaller loan — it usually means a cheaper one. Lenders price mortgages in loan-to-value (LTV) bands, and the best rates typically sit at 60%, 75%, 85% and 90% LTV. Crossing one of those thresholds is often worth more than the equivalent extra months of saving. The flip side: every month spent saving is a month of rent paid and a month of potential house-price movement, so the "right" answer is rarely "save the absolute maximum."

Common mistakes

• Budgeting only for the deposit and forgetting stamp duty, legal fees, survey, mortgage arrangement fee and removals.
• Saving in a current account when a Lifetime ISA or cash ISA would add interest (and, for the LISA, a 25% government bonus on up to £4,000/year for eligible first-time buyers).
• Counting on a parent's "gifted deposit" without a written gifted-deposit letter the lender will accept.
• Targeting 5% because it's the minimum, rather than checking what jumping to 10% or 15% would save on the mortgage.
• Forgetting that house prices may move while you're saving — your target is a moving line, not a fixed post.

Beyond the numbers

A realistic deposit plan budgets for everything that lands on completion day, not just the deposit itself. Stamp duty for non-first-time buyers, solicitor and conveyancing fees (typically £1,200–£2,000), a homebuyer's survey (£400–£1,000), mortgage product fees, removals and the unavoidable first-month spending on the new place — curtains, mattress, a working oven — together often add 3–5% of the purchase price on top of the deposit. A useful rule of thumb: alongside the deposit, build a separate "moving fund" of around £5,000–£10,000 and assume it will mostly be spent.

Related tools: Mortgage Calculator · Mortgage Affordability · Stamp Duty · Rent vs Buy