Mortgage Deposit Savings Calculator
Saving a deposit is, for most first-time buyers, the biggest hurdle to homeownership — often bigger than the mortgage itself. Our mortgage deposit savings calculator projects how long it will take to reach your target, factoring in interest on your savings, rising house prices, and the powerful boost of a Lifetime ISA if you use one.
Mortgage Deposit Savings Calculator
Work out how long it will take to save your target deposit — including the Lifetime ISA bonus if you use one.
The Moving Target Problem
One detail many deposit calculators miss is that your target is not fixed — if house prices rise while you are saving, the deposit you need (a percentage of the price) rises too. This calculator projects both your growing savings pot and the likely growth in your target property’s value over the same period, so you can see whether your saving rate is genuinely keeping pace, or whether rising prices could outrun your progress.
The Lifetime ISA Bonus, Explained Simply
A Lifetime ISA (LISA) adds a 25% government bonus on top of what you save, up to an annual contribution limit of £4,000 — meaning a maximum bonus of £1,000 a year. Save the full £4,000 in a tax year and the government adds £1,000, giving you £5,000 towards your deposit for that year alone. This bonus is one of the most valuable, underused tools available to first-time buyers, and this calculator lets you toggle it on to see the difference it makes to your savings timeline.
Key Deposit Thresholds Worth Knowing
The calculator shows how long it would take to reach several common deposit levels — 5%, 10%, 15%, 20%, 25% and 40% — because each threshold typically unlocks better mortgage rates as your LTV drops. Seeing all these milestones side by side often reveals a useful insight: saving for just a few extra months to cross from a 10% to a 15% deposit can sometimes save more in mortgage interest over 25 years than the extra months of saving actually cost you.
A Worked Example
Aiming for a 10% deposit on a £280,000 property (£28,000) with £5,000 already saved and £300 a month going in at 4.2% savings interest, reaching the target could take a little over 5 years without a LISA. Add the LISA bonus on qualifying contributions and that timeline can shorten meaningfully, since roughly a quarter of every LISA-eligible pound saved is effectively free from the government — a difference that compounds the longer you save.
Balancing Deposit Saving with Everyday Life
Saving a meaningful deposit while also managing rent, bills and everyday costs is genuinely difficult for many first-time buyers, and it is worth being realistic about the monthly amount you can sustain rather than picking an ambitious figure that quickly becomes unaffordable. Small, consistent contributions maintained over several years generally outperform sporadic larger payments that stop and start, both because consistency benefits from compounding and because it is far easier to stick to a habit than to a one-off resolution. Automating your saving — setting up a standing order the day you are paid, before you have a chance to spend it — is one of the simplest and most effective ways to keep a deposit plan on track over the years it typically takes to reach a target.
It is also worth reviewing your target deposit periodically rather than treating it as fixed from day one — as this calculator shows, both your savings growth rate and expected house price inflation directly affect how long the journey will realistically take, and revisiting the numbers every six to twelve months helps you catch early whether you are on track, ahead, or need to adjust your monthly contribution to stay on schedule.
Frequently Asked Questions
Can I use a Lifetime ISA for any property?
The LISA bonus for a first home applies to properties up to £450,000 in the UK, and you must not have owned a property anywhere in the world before, and typically need to have held the LISA for at least 12 months before using it.
What happens if house prices rise faster than I can save?
This is a genuine risk with a moving target — the calculator’s house price growth projection helps highlight this scenario so you can adjust your monthly saving, target area, or timeline accordingly, rather than being caught out.
Is a 5% deposit realistic?
Some mortgage products, including certain first-time buyer and guarantor schemes, do accept 5% deposits, though rates are typically higher and lender choice more limited than at 10% or above.
Should I keep my deposit savings in cash or invest them?
Most financial guidance suggests keeping deposit savings you plan to use within the next few years in cash or cash-like accounts (including a cash LISA), since investments can fall in value shortly before you need the money — timing risk that a shorter savings horizon makes harder to absorb.