How to calculate how much you can safely spend

Four subtractions, in order. Each one removes money that was never really available, and what survives is the figure you can plan a trip or a purchase around.

The calculation

income − fixed costs − savings and goals − known future costs = spendable

Step 1 — Income you can rely on

Take-home pay, after tax and pension. Include regular benefits or reliable second income. Leave out bonuses and overtime you can't count on; they're a bonus to the plan rather than part of it. If you're paid weekly or four-weekly, convert to a monthly figure rather than assuming four weeks is a month.

Step 2 — Fixed costs

Rent or mortgage, council tax, energy, water, broadband, phone, insurance, travel, childcare, subscriptions and minimum debt repayments. Anything that leaves whether or not you do anything.

Step 3 — Savings and goals

Treat what you intend to save as a cost, not as leftovers. Money that only gets saved if nothing else comes up usually doesn't get saved.

Step 4 — Known future costs, spread monthly

Annual insurance, MOT and servicing, Christmas, birthdays, a booked trip. Add up the year and divide by twelve. This is the step most budgets skip, and it's the one that causes the "where did it go?" months.

A worked example

Worked example of spendable money
Monthly income after tax	£2,000
Fixed costs	− £1,200
Savings and goals	− £200
Known future costs (£3,360 a year ÷ 12)	− £280
Spendable	£320 a month

£320 a month is £960 over three months and £3,840 over a year. A £1,200 holiday four months away needs £300 a month set aside, which leaves £20 a month for everything else — technically possible, uncomfortable in practice. Six months away, it's £200 a month and far more realistic.

Common mistakes

Using gross pay instead of take-home.
Counting only monthly bills and forgetting the yearly ones.
Treating savings as whatever survives the month.
Planning from your account balance, which still contains money that's already promised.

Questions people ask

How do I work out how much I can spend a month?

Take your monthly income after tax, subtract fixed costs, subtract what you're putting into savings and goals, then subtract a monthly share of the irregular costs you already know about. What's left is what you can plan around.

Why subtract yearly bills every month?

Because they're not optional and they don't arrive evenly. Spreading a £600 annual insurance bill as £50 a month means the month it lands isn't a shock.

Is the result guaranteed?

No. It's an estimate based on the figures you enter and assumes your income and costs stay roughly the same. It's a planning tool rather than financial advice.

The full method, including how the app handles pay cycles and sub-goals, is on the methodology page.