Zero-Based Budget Calculator
The income, and every job you give it
Your result will appear here
Fill in the fields on the left and this updates as you type.
Know what this estimate is based on
- Jurisdiction
- General mathematical model
- Scope and limitations
- Planning estimate only. Enter complete, current figures and keep an appropriate buffer for irregular or unexpected expenses.
- Source links checked
- Jul 30, 2026
Built and regression-tested by Smart Tools Lab. It has not been individually reviewed by a licensed financial, tax, or legal professional.
How to use
- 01
Enter your monthly take-home pay — the number that actually lands in the account, after tax and after anything your employer deducts — plus any other income arriving this month.
- 02
Fill the seven bill lines: housing, utilities, groceries, transportation, insurance and medical, childcare and support, and the minimum payments on every debt you carry.
- 03
Enter one figure for discretionary spending — restaurants, subscriptions, hobbies, gifts, travel — as a single line you are choosing rather than a leftover.
- 04
Give the future its three lines too: savings and investing, sinking funds for the bills that are not monthly, and any extra debt payment above the minimums.
- 05
Read the headline. Anything still to assign is money with no name on it, and anything over-assigned is a plan that does not fit — the table below shows the remainder falling line by line so you can see exactly where it ran out.
Formula
Income = take-home pay + other income. Assigned = housing + utilities + groceries + transportation + insurance and medical + childcare + debt minimums + discretionary + savings + sinking funds + extra debt payments. Left to assign = income − assigned, and the budget is finished when that reaches zero. The table walks the same subtraction one line at a time so the running remainder is visible: start at the income, subtract each line in turn, and the last figure in the column is the headline.
Example
$6,200 of take-home pay and no other income. The bills take $4,220 — $1,900 housing, $380 utilities, $650 groceries, $520 transportation, $340 insurance and medical, nothing for childcare, and $430 of debt minimums, which is 68% of income before a single discretionary dollar is spent. Discretionary spending takes $640 and the future takes $1,250: $700 to savings, $250 to sinking funds and $300 as an extra debt payment. That is $6,110 assigned against $6,200 of income, so $90 is still waiting for a job — $1,080 a year, and precisely the kind of amount that never survives contact with a month. Move it to the savings line and the budget reaches zero.
Definitions
- Left to assign
- Income minus every job you have given it. Positive means money with no name on it; negative means the plan is bigger than the income behind it. Zero is the finished state.
- Debt minimum
- The smallest payment the lender will accept this month. It is a bill rather than a choice, which is why it sits with the other bills and not with the savings.
- Sinking fund
- A monthly set-aside for a cost that is certain but not monthly — registration, an annual premium, the holidays. It converts a future lump into a line in this month's budget.
- Residual saving
- Saving whatever is left at the end of the month. It is the habit zero-based budgeting exists to break, because across twelve months the leftover averages close to nothing.
Good to know
Every dollar gets a job, which is not the same as spending it
Zero-based budgeting is one rule: income minus every assignment equals zero. It began as a corporate technique — Peter Pyhrr developed it at Texas Instruments in the late 1960s, on the principle that every line of a departmental budget should be justified from nothing each cycle rather than inherited from last year with a percentage on top — and it transferred to household finance almost unchanged. The household version keeps the same insistence: no line exists because it existed last month, and nothing is left unexamined. The misunderstanding that stops people trying it is the word zero. It does not mean the account is emptied, and it does not mean every dollar is consumed. Savings, sinking funds and extra debt payments are jobs exactly like groceries are; a plan that assigns $700 to investing and $250 to a car fund has reached zero with $950 still sitting in the bank. What zero-based budgeting refuses is not saving but the residual — the arrangement where saving is defined as whatever survives the month. That is the whole of the difference, and it is a large one.
Why the leftover never survives
Almost every budget that fails does so in the same way. Income is listed, the known bills are listed, and the difference is labelled savings — implicitly, as an expectation rather than as an instruction. The month then happens, and the difference turns out to be smaller than expected, because unassigned money in a checking account does not feel like anything in particular. It looks like slack. A $90 gap between what you earn and what you have consciously assigned is not experienced as $90; it is experienced as being slightly comfortable, and being slightly comfortable reliably costs about $90. Across a year that is $1,080 that nobody decided to spend and nobody decided to save. The remedy is not discipline and it is not tracking, both of which happen after the money is gone. It is naming the destination before the month starts, so that spending it requires overriding a decision rather than merely failing to make one. That single change of order — assign first, spend second — is most of what separates households who save from households on the same income who do not.
The two lines to keep apart, and the one line most budgets omit
Debt appears twice in this calculator, and merging the two is one of the quiet ways a budget misleads its author. A minimum payment is a bill: it arrives whether or not you plan for it, and it belongs beside the rent and the utilities. An extra payment above the minimum is a strategy: it is money you have chosen to send to a lender instead of to savings, and it is reversible in a hard month in a way that a minimum is not. Collapsed into one debt line, a budget can look balanced while concealing which half is obligation and which half is choice, and when the month gets tight the wrong half is usually the one that gets cut. The other structural point is what is missing. Most household budgets have no line for costs that are certain but not monthly — car registration, an insurance renewal, tires, property tax, the holidays. Those costs balance perfectly in January and break the plan in March, when a certainty arrives dressed as an emergency. A sinking-fund line is what converts them from a shock into a subtraction.
Rewriting it, and what the first three months look like
A zero-based budget is written monthly rather than rolled forward, and that is the practice rather than a chore attached to it. The month is what changed: a birthday, an annual renewal, a quarter that happens to carry two insurance bills, a school year that starts. The categories stay put and only the amounts move, so once the lines exist the rewrite takes about ten minutes. Expect the first three months to be wrong. Everyone underestimates food and everyone underestimates the small recurring charges, and the fix is not to try harder but to build the next month's numbers from last month's actual statements instead of from memory. By the third pass the estimates converge, and from then on the budget stops being a prediction and becomes a decision. Two habits make the difference stick: reconcile against the bank once a week rather than at month end, so a category that has run over is caught while there is still time to move money from another one; and when something genuinely unplanned happens, move the money from a named line rather than pretending the budget still holds. Adjusting is using it correctly. Abandoning it is not.
Frequently asked questions
What is a zero-based budget?
A budget where income minus every assignment equals exactly zero. It is not a spending plan that empties the account — savings, sinking funds and debt payoff are jobs like any other. What it refuses is a residual: a budget where saving is whatever happens to be left at the end of the month, which across a year is reliably nothing.
Why does it matter if a little is left unassigned?
Because unassigned money is not saved money. It sits in the checking account looking like slack and gets absorbed by the month without ever appearing as a decision. $90 left over every month is $1,080 a year that nobody chose to spend and nobody chose to save. Give it a name, even if the name is just savings.
What if I have assigned more than I earn?
That is the useful failure, and it is better to meet it on a Sunday afternoon than on the 27th of the month. The plan is over before the month starts and the choice is now explicit: cut the overage from somewhere on the list, or the month makes the cut for you, on a credit card, at the end of it.
Why are debt minimums and extra debt payments separate lines?
Because they are different kinds of money. The minimum is a bill that arrives whether you plan for it or not — an obligation. The extra payment is a choice you are making with money that could have gone to savings — a strategy. Merged into one line, a budget can look balanced while hiding which half is which, and the first thing that gets cut in a hard month is usually the wrong half.
Do I have to redo this every month?
Yes, and that is the method rather than a chore. The month is what changed: a birthday, an annual renewal, a quarter with two insurance bills in it. The lines stay the same and only the amounts move, so a rewrite takes about ten minutes once the categories exist. A budget filled in once and rolled forward is a spreadsheet, not a plan.
What income figure should I use if my pay varies?
The lowest of the last three months, not the average. A zero-based budget assigns income you have rather than income you expect, and assigning an average in a month that did not deliver it produces a shortfall you cover with debt. If your income genuinely swings — commission, freelance, gig work — the irregular-income page finds the steady number to budget on first, and then this page assigns it.
Where do irregular bills like car registration go?
On the sinking-fund line, as a monthly set-aside rather than as the bill itself. Registration, an insurance renewal, tires and the holidays are all certain and none of them is monthly, so a budget with no sinking-fund line balances in January and breaks in March, when the certain cost arrives looking like an emergency.