House deposit calculator: how long to save 2.5% or 5%

What this deposit calculator shows

Type the price of the home and the calculator shows the 2.5% deposit in pounds, the monthly mortgage that goes with it, how long the deposit takes to save at the amount you enter under “More options”, and the same timeline inside a Lifetime ISA with the government’s 25% bonus (GOV.UK). It also shows the stamp duty on that price, which for most first-time buyers below £300,000 is nothing (GOV.UK).

The 2.5% figure comes from the government’s announcement of the scheme and is marked “Announced, detail to come” until the Budget confirms it on 28 October 2026 (GOV.UK). If the Budget changes it, the calculator changes the same day.

Reading the savings timeline

The plain timeline divides the deposit by your monthly saving and rounds up to whole months. It ignores interest on your savings, which at today’s rates adds a month or two of help on a two-year plan, and it ignores pay rises, so the real timeline should be a little shorter. Treat it as the longest it should take.

The Lifetime ISA timeline adds 25% to every pound you save up to £4,000 a year (£333 a month). Above that, the extra saving earns no bonus, so the calculator only boosts the first £333 of each month. A person saving £300 a month reaches £5,750 in 16 months instead of 20. A person saving £800 a month would have the money in about 7 months, but a Lifetime ISA cannot be used for a purchase until 12 months after the first payment in (GOV.UK), so the calculator shows 12 months and says why. The Treasury has also consulted on a new First-Time Buyer ISA to be offered “in place of the Lifetime ISA” once it exists (GOV.UK); the Lifetime ISA page explains what that means for savers.

How much should you save each month?

Work backwards from when you want to buy. The table shows how long the two most common targets take on a £230,000 home, in months, with the Lifetime ISA column applying both the 25% bonus (on up to £333 a month) and the rule that the account must be open for 12 months before you use it (GOV.UK). Interest on savings is ignored, so real timelines are slightly shorter.

Two lessons from the table. First, the Lifetime ISA bonus helps most on slow, steady saving, because the bonus is capped at £1,000 a year and the 12-month rule bites when you save fast. Second, the gap between a 2.5% and a 5% deposit is about a year and a half at £300 a month, which is the practical meaning of the Your First Home deposit for anyone who cannot rely on a gift. The scheme needs 2.5%, but the “Your deposit” box accepts any figure up to 50% if you want to see what a bigger deposit does to the mortgage; the deposit guide weighs up whether putting down more is worth it. Before adding to a deposit, MoneyHelper’s rule of thumb is to hold “three to six months’ essential outgoings” as an emergency fund (MoneyHelper).

What if prices rise while you save?

A deposit target moves. If new-build prices rose 3% in a year, a £230,000 home would cost about £236,900, and 2.5% of it about £5,920, so the target grows by roughly £170 a year; at £300 a month you save £3,600 a year, so you still gain on it comfortably. The bigger risk is a 5% target, which grows twice as fast. Use the growth box under “More options” to see what a price rise does to the repayment on the equity loan as well; the equity loan calculator is built around that question.

What the deposit does not cover

Legal fees, searches, a snagging survey, the developer’s reservation fee, mortgage fees and moving costs all sit on top. On a £230,000 home, expect the total cash needed to be about £10,300 rather than £5,750 (our itemised example comes to £4,548 of costs on top of the deposit). The deposit page breaks this down with sources, and the first-time buyer costs guide goes line by line.