Personal Monthly Budget Calculator
Build a monthly budget from income and spending tagged as needs, wants or savings, compared with the 50/30/20 guideline.
Your inputs
Results
Left over (unallocated)
$1,550.00
- Total income
- $4,500.00
- Total allocated
- $2,950.00
- Needs (50/30/20 guide: 50 %)
- 45.56%
- Wants (guide: 30 %)
- 6.67%
- Savings and debt payoff (guide: 20 %)
- 13.33%
✓Exact calculation — rounded only for display
Notes for this result
- The 50/30/20 split is a popular rule of thumb, not a requirement; adjust it to your circumstances.
| Category | Type | Amount | Of income |
|---|---|---|---|
| Rent | need | $1,400.00 | 31.1% |
| Groceries | need | $450.00 | 10% |
| Transport | need | $200.00 | 4.4% |
| Dining out | want | $250.00 | 5.6% |
| Subscriptions | want | $50.00 | 1.1% |
| Savings | save | $600.00 | 13.3% |
What this calculator does
A budget shows where money goes. Tagging each line makes it easy to compare with the popular 50/30/20 rule.
Formula and method
Worked example
Calculated by this tool with its default inputs:
Inputs
- Monthly income after tax — one per line: source, amount: Salary, 4000 Side work, 500
- Monthly spending — one per line: category, amount, need / want / save: Rent, 1400, need Groceries, 450, need Transport, 200, need Dining out, 250, want Subscriptions, 50, want Savings, 600, save
Results
- Left over (unallocated): 1,550
- Total income: 4,500
- Total allocated: 2,950
- Needs (50/30/20 guide: 50 %): 45.56%
- Wants (guide: 30 %): 6.67%
- Savings and debt payoff (guide: 20 %): 13.33%
How to read the results
A positive amount left over can go to savings or debt; a negative amount needs action.
Assumptions and limitations
- 50/30/20 is a rule of thumb, not a requirement; adjust for your situation.
- Use after-tax income.
Quantities and costs are planning estimates. Add sensible allowances, and check with suppliers, carriers or professionals before buying, shipping or building.
Questions
What counts as a need?
Essentials you must pay — housing, utilities, basic food, transport and minimum debt payments.
Methodology and verification
- Result type
- Exact mathematical calculation (rounded only for display)
- Formula version
- 1.0
- Automated verification
- 3 reference and validation test cases, checked against independently computed values. The site cannot be built if any of them fail.
- Editorial review
- Awaiting human editorial review. The explanation was drafted with AI assistance; the formula and examples are verified by the automated tests above.
Privacy
Everything you enter is calculated in this browser and is not sent to Numerith or anyone else. Inputs are added to a share link only if you choose to include them. Privacy policy