Lean FIRE targets early retirement with below-average spending — typically under $40,000/year for a single person.
Lean FIRE requires less savings but more frugality. Target: 25× your lean annual expenses.
This calculator earns its keep at decision points: before accepting a loan, comparing investment platforms, or negotiating salary. The difference between the headline figure and the true cost or return is only visible with accurate arithmetic.
A frequent error is using annual rates where monthly rates are required (or vice versa). Simply dividing an annual rate by 12 is only an approximation — the correct conversion for compound calculations uses the (1 + r)^(1/12) − 1 formula.
An employee receives a counter-offer from another employer: a £4,000 salary increase but no pension contribution versus the current role's lower salary with 8% employer pension. Running both through the finance calculator shows the true net financial value of each offer.
Early retirement on a minimalist budget — typically under $40K/year for a single person.