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50/30/20 Budget Calculator
Splits monthly after-tax income into needs, wants and savings/debt repayment with the 50/30/20 rule (Warren & Tyagi, All Your Worth, 2005) or custom percentages, and compares the targets with current spending when it is given.
When to use
You want target amounts for essentials, discretionary spending and savings from take-home pay, or to check how far current spending deviates from the 50/30/20 split.
Do not use when: You need the time or deposit to reach a savings target (use savings-goal), a debt payoff schedule (use debt-payoff), or a line-item budget. Informational; not financial advice.
Formula
needs_budget = income × needs_percent/100; wants_budget = income × wants_percent/100; savings_budget = income × savings_percent/100; annual_savings = savings_budget × 12; x_difference = x_budget − current_x; current_x_percent = current_x / income × 100
The 50/30/20 rule from Warren & Tyagi's All Your Worth (2005) applies to after-tax income and treats minimum debt payments as needs and extra repayments as savings; it is a rule of thumb, not a prescription, and custom percentages (e.g. 60/20/20 in high-cost cities) are accepted as long as they sum to 100.
Inputs
| Parameter | Type | Unit | Required | Description |
|---|---|---|---|---|
monthly_after_tax_income | number | yes | Take-home pay per month after income tax and payroll deductions (add back retirement contributions withheld at source if you count them as savings). Range: > 0, ≤ 1000000000 | |
needs_percent | number | % | default 50 | Share for essentials: housing, utilities, groceries, insurance, minimum debt payments, transport to work. Range: ≥ 0, ≤ 100 |
wants_percent | number | % | default 30 | Share for discretionary spending: dining out, entertainment, travel, subscriptions. Range: ≥ 0, ≤ 100 |
savings_percent | number | % | default 20 | Share for savings, investments and debt repayment beyond the minimums. The three shares must sum to 100. Range: ≥ 0, ≤ 100 |
current_needs | number | no | What you currently spend on needs per month, for comparison. Range: ≥ 0, ≤ 1000000000 | |
current_wants | number | no | Current monthly discretionary spending. Range: ≥ 0, ≤ 1000000000 | |
current_savings | number | no | Current monthly savings and extra debt repayment. Range: ≥ 0, ≤ 1000000000 |
Outputs
| Output | Type | Unit | Description |
|---|---|---|---|
needs_budget | number | monthly_after_tax_income × needs_percent / 100. | |
wants_budget | number | monthly_after_tax_income × wants_percent / 100. | |
savings_budget | number | monthly_after_tax_income × savings_percent / 100. | |
annual_savings | number | savings_budget × 12. | |
needs_difference | number | needs_budget − current_needs (positive = under budget; only when current_needs is given). | |
wants_difference | number | wants_budget − current_wants (positive = under budget; only when current_wants is given). | |
savings_difference | number | savings_budget − current_savings (positive = saving less than the target, i.e. a shortfall; only when current_savings is given). | |
current_needs_percent | number | % | current_needs / income × 100 (when given). |
current_wants_percent | number | % | current_wants / income × 100 (when given). |
current_savings_percent | number | % | current_savings / income × 100 (when given). |
assessment | string | Plain-language comparison of current spending with the targets. |
Example
4,000 take-home per month, default 50/30/20: {"monthly_after_tax_income":4000} → {"needs_budget":2000,"wants_budget":1200,"savings_budget":800,"annual_savings":9600}
6,500 per month, currently spending 3,500 / 1,800 and saving 1,200: {"monthly_after_tax_income":6500,"current_needs":3500,"current_wants":1800,"current_savings":1200} → {"needs_budget":3250,"wants_budget":1950,"savings_budget":1300,"annual_savings":15600,"needs_difference":-250,"wants_difference":150,"savings_difference":100,"current_needs_percent":53.85}
GET https://tttkmbb.com/api/v1/calculate/budget-50-30-20?monthly_after_tax_income=4000
Machine access
- API:
GET https://tttkmbb.com/api/v1/calculate/budget-50-30-20(query parameters) orPOSTwith a JSON body{"inputs": {...}} - Schema: https://tttkmbb.com/api/v1/calculators/budget-50-30-20 · Markdown: https://tttkmbb.com/finance/budget-50-30-20.md · JSON definition: https://tttkmbb.com/finance/budget-50-30-20.json
- MCP: server
https://tttkmbb.com/mcp, toolrun_calculator with calculator_id="budget-50-30-20" - OpenAPI operationId:
calculate_50_30_20_budget - Freshness:
static. Authentication: none. Rate limit: fair use (see rate limits).
Sources
FAQ
Is the income before or after tax?
After tax (take-home pay). The rule was defined on after-tax income; if retirement contributions are deducted from your paycheck before you see it, add them back to income and count them as savings.
Where do debt payments go?
Minimum required payments are needs (they are not optional); anything paid above the minimum counts toward the 20 % savings/debt-repayment share.
What if my needs exceed 50 %?
Common where housing is expensive. Adjust the shares (e.g. 60/20/20) to keep the savings share, or treat the excess as a signal to lower fixed costs; the rule is a guideline, not a requirement.
Related calculators
- Savings Goal Calculator — Turn the savings target into a timeline for a specific goal.
- Debt Payoff Calculator — Apply the savings share to clear a balance faster.
- Salary Converter — Convert an annual salary into monthly pay before budgeting.