Budget Calculator

What this budget calculator does

A budget starts with the money that comes in and subtracts the money that goes out. This calculator normalizes every income and expense item to an annual figure, applies a single effective tax rate to income, and shows the monthly and annual balance. It also groups expenses so you can see where the money goes and calculates two common debt-to-income ratios.

The output is a planning snapshot, not a bank statement. It is most useful when you enter realistic recurring amounts and update them when your situation changes.

How to use this calculator

1. Enter each income source and choose whether the amount is monthly or annual.
2. Enter your effective tax rate. This is the share of gross income that goes to income and payroll taxes, not just the top marginal rate.
3. Enter expenses in each group. Use the monthly or annual selector for each item.
4. Click Calculate to see before-tax income, after-tax income, total expenses, the surplus or deficit, and the expense breakdown.

The default example is a household with $80,000 in salary, $1,000 in investment income, $2,000 in other income, a 28% tax rate, and a mix of housing, transportation, living, debt, healthcare, education, savings, and miscellaneous costs.

Budget formulas

Annual income = Σ (income item × 12 if monthly, otherwise as entered)
After-tax income = Annual income × (1 − Tax rate ÷ 100)

Housing = Mortgage + Property tax + Rent + Home insurance
        + HOA + Maintenance + Utilities
Transportation = Auto loan + Auto insurance + Gasoline
               + Auto maintenance + Parking and tolls + Other transportation
Living = Food + Clothing + Grocery + Meals out + Other living
Other debt = Credit card + Student loan + Other loan
Healthcare = Medical insurance + Medical spending
Education = Childcare + Tuition + Child support + Other education
Savings = (401(k)/IRA + College saving) × (1 − Tax rate ÷ 100)
        + Stocks and bonds + Other savings
Miscellaneous = Pet + Gifts + Hobbies + Entertainment + Vacation + All other

Total expenses = Housing + Transportation + Living + Other debt
               + Healthcare + Education + Savings + Miscellaneous
Net = After-tax income − Total expenses

The 401(k)/IRA and college saving amounts are adjusted by the tax rate because they are typically funded with pre-tax dollars. The debt row in the display includes the mortgage and auto loan so you can compare it with the reference layout, but the total counts those items once, inside housing and transportation.

Debt-to-income ratios

Housing debt = Mortgage + Property tax + Rent + Home insurance + HOA
Front-end DTI = Housing debt ÷ Gross annual income

Total debt = Housing debt + Auto loan + Credit card
           + Student loan + Other loan
Total DTI = Total debt ÷ Gross annual income

Both ratios use gross income. The front-end ratio focuses on housing costs; the total ratio adds the other recurring debt payments. Utilities and maintenance are not included in the DTI numerator, even though they are part of the housing budget.

What the results mean

• Before-tax income: all income sources before tax.
• After-tax income: the amount available to spend and save after the effective tax rate.
• Total expenses: the sum of the recurring expense groups.
• Net (deficit): what is left over, or how much the budget is short, each month and each year.
• Expense breakdown: each group's annual amount, monthly amount, and share of after-tax income.
• DTI ratios: a lender-style view of housing and total debt relative to gross income.

The percentages in the breakdown use after-tax income as the denominator, so they show how each group consumes the money you actually have available.

Assumptions and limitations

The calculator uses one effective tax rate for all income and does not model brackets, credits, deductions, state taxes, or payroll tax caps. It treats every input as a recurring amount and does not handle one-time windfalls, irregular self-employment income, or seasonal expenses. It does not connect to bank accounts or verify the amounts.

The expense groups are a planning structure, not an accounting standard. Some items can reasonably be placed in more than one group. The DTI calculation follows the simplified definition above and may differ from a lender's underwriting model, which can include other obligations or use a different income figure.

Frequently asked questions

Should I enter monthly or annual amounts?

Use whichever number you know. The calculator converts monthly amounts to annual by multiplying by 12, and leaves annual amounts as entered. The result always shows both monthly and annual figures.

Why are 401(k) and college saving adjusted for taxes?

Those contributions are often made with pre-tax dollars. Adjusting them by the tax rate puts them on a comparable after-tax basis with the other expenses, so the budget does not overstate their impact on take-home pay. Employer matches and vesting are not included.

What counts in the DTI ratio?

The front-end ratio includes mortgage, property tax, rent, home insurance, and HOA dues. The total ratio adds auto loan, credit card, student loan, and other loan payments. Utilities, maintenance, food, and other living costs are excluded.

Why is my budget negative?

A negative result means the recurring expenses you entered exceed after-tax income. That can be a temporary month, a data-entry issue, or a structural gap. Review the largest categories first and compare the amounts with several months of actual statements.

Source

References:

• Consumer Financial Protection Bureau — Money as You Grow
• Consumer Financial Protection Bureau — What is a debt-to-income ratio?

Disclaimer

This calculator is for informational and educational purposes only. It is not financial, tax, or investment advice. A budget based on estimates can differ from your actual cash flow. Review your statements and consult a qualified adviser for decisions about debt, taxes, or retirement.