Put your real numbers in. Get an honest answer — deposit timeline, monthly mortgage vs rent, 5-year cost comparison, and whether your income can support the purchase.
Based on real London property pricesNo AI tokens wasted on simple mathsTakes 60 seconds
How this works — the thinking flow
1
Your rent situationWhat you pay now — your baseline cost of housing.
2
Your savings powerYour income and how much you can set aside each month toward a deposit.
3
Your target propertyWhat you want to buy and how much deposit you're aiming for.
4
Your mortgageThe rate and term you'd borrow on — we run the maths for you.
🏠
1 — Your Rent
What you pay today
£/mo
Your current monthly rent payment
yrs
Used to calculate rent already paid
💰
2 — Your Savings
Income & what you can set aside
£/yr
Used to check mortgage affordability (income × 4.5)
£/mo
How much you can put aside each month
£
What you've saved so far toward a deposit
% p.a.
Leave at 4.5% for a typical cash ISA
🏡
3 — Your Target Property
What you want to buy
£
Use OpenProp to find the lower quartile price in your borough — that's your realistic entry price
%
5% is the minimum for most lenders. 10–15% gets you better rates.
🏦
4 — Your Mortgage
Borrowing assumptions
% p.a.
Current 2-year fixed rates are typically 4–5%. Check MoneySupermarket for live rates.
yrs
Longer term = lower monthly payment but more interest paid overall
All calculations run locally in your browser. Nothing is sent to a server.
1
The cost of renting — what you've spent and what's ahead
This money is gone. It built no equity, no asset.
Rent already paid monthly rent × 12 × years renting—
Annual rent cost monthly rent × 12—
Projected rent over next 5 years monthly rent × 60 months—
2
The deposit challenge — how long until you can buy
With compound interest on your savings, and what renting costs while you wait
Deposit required property price × deposit %—
Already saved your input—
Still to save deposit required − savings already accumulated—
Time to reach deposit n = log((D + S÷r) ÷ (A + S÷r)) ÷ log(1+r) — D=deposit, S=monthly savings, A=existing savings, r=annual rate÷12—
Rent paid while saving monthly rent × months to save—
3
The mortgage — what you'd pay each month once you buy
Based on your rate, term, and loan amount
Loan amount property price − deposit—
Monthly mortgage payment PMT = L × r × (1+r)ⁿ ÷ ((1+r)ⁿ − 1) — L=loan, r=annual rate÷12, n=term in months—
Total interest paid over full term (monthly payment × term months) − loan amount—
4
Renting vs buying — the monthly comparison
Once you've bought, is the mortgage cheaper than what you pay in rent today?
In the print dialog, choose "Save as PDF" as the destination
Formulas used in this calculatorDeposit timeline: n = log((D + S÷r) ÷ (A + S÷r)) ÷ log(1+r) — D = deposit needed, S = monthly savings, A = existing savings, r = annual rate ÷ 12. Both the lump sum and monthly contributions are compounded. Monthly mortgage payment: PMT = L × r × (1+r)ⁿ ÷ ((1+r)ⁿ − 1) — L = loan, r = annual rate ÷ 12, n = term in months. Standard repayment annuity formula. Total interest (full term): (monthly payment × term months) − loan amount. Equity after 5 years: deposit + principal repaid, calculated via iterative month-by-month amortisation over 60 months. Each month: interest = balance × r; principal repaid = payment − interest; balance reduced accordingly. 5-year interest cost: (monthly payment × 60) − principal repaid in 60 months. Affordability (max mortgage): income × 4.5 — rule of thumb only; actual lender criteria vary by provider, income type, and outgoings.
⚠️ This calculator is illustrative only. It uses simplified assumptions: a fixed mortgage rate for the full term, no stamp duty, legal fees, survey costs, or ongoing maintenance included, and an income × 4.5 affordability rule of thumb (actual lender criteria vary). It does not constitute financial, mortgage, or property investment advice. Always speak to a qualified mortgage broker before making any purchase decision.