Monthly Budget Calculator
See how much cash is left after monthly expenses
Result
How it is calculated
The tool adds the four expense categories, expenses = housing + transport + food + other, then subtracts them from income: leftover = income − expenses. The savings rate is leftover ÷ income × 100. All amounts are per month and must be in the same currency; the tool only does arithmetic and shows amounts with a dollar sign. Income must be above zero, and every expense field must be filled with a number of zero or more, so enter 0 for an unused category: an empty field gives no result. If you spend more than you earn, leftover and savings rate come out negative, which shows the monthly shortfall.
Worked example
Monthly income is 4,500. Housing 1,500, transport 400, food 600 and other 500. Expenses: 1,500 + 400 + 600 + 500 = $3,000.00. Leftover: 4,500 − 3,000 = $1,500.00. Savings rate: 1,500 ÷ 4,500 × 100 = 33.33%. If other spending rose to 2,000, expenses would reach 4,500 and the leftover would be zero.
Common mistakes
- Entering annual figures in some fields and monthly in others. Rent paid yearly or an annual insurance premium should be divided by 12 first.
- Entering gross income instead of the amount that actually reaches your account, which overstates what is left.
- Leaving a category empty instead of typing 0, and getting no result.
- Forgetting irregular costs such as subscriptions, gifts or repairs, which belong in "other". The leftover then looks larger than it really is.
- Reading the leftover as spare money. If you have debt payments or savings goals, they must come out of it.
Sources
- 6.5 Making a Personal Budget - Contemporary Mathematics — OpenStax, Rice University
About this calculator
This calculator takes a straightforward income-minus-expenses approach: it sums your expense categories — housing, transportation, food and other expenses — and subtracts that total from your monthly income to show exactly what's left over, and what share of your income that is, whether that's a surplus to save or invest, or a shortfall that means something has to give.
Financial coaches recommend building this breakdown before setting any savings goal, because it turns a vague sense of "money feels tight" into concrete numbers by category, making it obvious which expense line is actually eating the budget rather than guessing.
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Comments (1)
Irregular costs are the usual reason a budget looks better on paper than in your account. Annual bills such as insurance, subscriptions or holiday spending belong in the monthly figure as one twelfth, and the tool only sees the four categories you fill in. Enter 0 for any you skip. Where does your month most often leak money, and which extra category would you like to see?