First We Plan is a free, browser-based mortgage and household affordability calculator for UK homebuyers, built by Bookrightly. It works out your deposit, monthly mortgage payment, total interest and loan-to-value ratio, then walks through a full essential-vs-optional household expense breakdown, an emergency fund target and a recommended monthly savings plan — finishing with a plain-English affordability verdict and a downloadable PDF summary.
It calculates your estimated deposit, monthly mortgage payment, total interest and loan-to-value ratio, then combines that with a full breakdown of essential and optional household expenses, an emergency fund target and a recommended monthly savings plan to give you a plain-English affordability verdict: Comfortable, Manageable, Tight or High Risk.
Using the standard amortising loan formula based on your home price, deposit, interest rate and mortgage term — or, for interest-only mortgages, interest on the outstanding balance alone.
Essentials include your mortgage, council tax, utilities (gas, electricity, water, internet), home insurance, maintenance, car costs, groceries, childcare, school costs and existing debt repayments. Optional spending includes subscriptions, entertainment, eating out, hobbies and similar lifestyle costs. This split drives the emergency fund target, which is based on essential spending only.
The calculator targets your essential monthly expenses multiplied by a safety margin you choose (3, 6, 9 or 12 months), then shows a recommended monthly savings amount to close the gap between that target and your existing savings over a timeframe you set.
Income reduction, mortgage rate increases, an added child, food and energy price rises, overtime disappearing, a relationship breakdown, and one-off costs like car or home repairs — each recalculated against your own numbers so you can see how your affordability status changes.
No. It's a planning tool for estimates only — not mortgage advice, a mortgage offer, or a guarantee of affordability. Actual lender criteria, rates and approval decisions vary.
No account is needed. All calculations run entirely in your browser; your figures are stored only in your own browser's local storage and are never sent to a server.
Yes, it's free to use with no sign-up required.