How to use the budget calculator
Enter your monthly income after tax, then what you spend in each group. Leave any line that doesn't apply empty. The calculator shows what's left over, how your spending splits between needs, wants and savings, and how that compares with the 50/30/20 rule.
The 50/30/20 rule
Needs ≈ 50% of take-home pay
Wants ≈ 30%
Savings and extra debt payments ≈ 20%
This guideline was popularised by Elizabeth Warren and Amelia Warren Tyagi in their 2005 book All Your Worth. It's a starting point, not a rule you must follow: in expensive cities, rent alone can take half of take-home pay.
- Needs are costs you'd struggle to cut: housing, utilities, basic groceries, transport to work, insurance and minimum debt payments.
- Wants are the rest: eating out, entertainment, subscriptions, shopping and holidays.
- Savings include emergency savings, retirement and investing, and paying off debt faster than the minimum.
Worked example
Take-home pay of 5,000 a month. Needs total 2,750 (55%), wants 570 (11.4%), savings 700 (14%), so 980 is left over.
Compared with 50/30/20, needs are a little high and savings a little low. Moving the 980 left over into savings would bring savings to 33.6%.
See the bigger picture with the net worth calculator.
Frequently asked questions
Should I budget with income before or after tax?
After tax: the money that actually reaches your bank account.
What if my income changes each month?
Budget with a cautious, lower month, and save what you earn above it.
Formulas checked 29 October 2026. How we test our calculators. This calculator is for planning and education, not financial, tax or legal advice.