How the numbers are calculated, and how they are checked

Definitions

Weeks of cash

How many weeks your cash lasts at the pace in your forecast. It is read from the week your ending cash first reaches zero.

Cash floor

Months of fixed costs times your monthly fixed costs. The workbook default is 2 months; the cell is yours to change. In the simulator the floor is two months of the fixed costs you enter.

Low point, and the week it falls in

The lowest ending cash in the 13 weeks, and the week number where it happens.

Weeks under the floor

How many projected weeks end with cash below the floor.

"If sales stopped tomorrow"

The weeks your cash plus money owed to you, minus unpaid bills, would cover your fixed costs with no new sales.

The variance flag

A line that misses in the same direction three weeks running.

Days to get paid, days stock sits, days you take to pay, and the cash conversion cycle

How long customers take to pay you, how long stock sits before it sells, how long you take to pay suppliers, and the days your cash is tied up between paying out and getting paid.

How the simulator calculates

Each week: balance = last week's balance + cash in - cash out. The chart shows 26 weeks.

Cash floor: two months of the monthly fixed costs you entered. Fixed costs are assumed to be inside "cash out per week" already; here they only set the floor.

Weeks of cash: the week the balance reaches zero, to one decimal. If it does not reach zero in 26 weeks, the pace of the last four weeks is carried forward. If cash is not falling, the gauge shows ∞ (and anything beyond a year is shown as 52+).

Weeks below the floor: how many of the 26 projected weeks end under the floor.

The decisions: Hire: 5,000 a month from week 4. Revenue drops 30%: cash in is 30% lower from week 1. Buy 20k inventory: one payment of 20,000 in week 2. Top client pays a month late: 45% of cash in for weeks 1 to 4 arrives in weeks 5 to 8. Collect 10 days faster: about 10 days of cash in arrives once, in week 1. Raise prices 15%: cash in is 15% higher from week 5 (invoices already sent keep the old price; no customers lost).

What this is not: a forecast of your business. It extends the numbers you type. The full workbook builds the 13 weeks line by line.

How the workbook calculates weeks of cash

1. If cash today is zero or less, the answer is 0.
2. If the 13-week forecast reaches zero, it is the week it first does, to a fraction of a week.
3. If the average weekly net cash is zero or positive, it is shown as 52+.
4. Otherwise it is 13 plus ending cash divided by the average weekly burn, capped at 52+.

The free starter uses the same chain.

Read a formula in the file

These are six real cells of the DASHBOARD tab of the example workbook. The formula bar shows the formula exactly as it is in the file.

How it is tested

Before a number appears on this site, it is recalculated from the workbook's own formulas. The workbook has 324 formulas. The example business's dashboard, 13-week line, scenario test, variance log and working-capital figures were each reproduced by hand from the shipped inputs and match what the file shows. The simulator's results were compared across 22,980 input combinations before and after the most recent rounds of changes, with no differences in the numbers it shows. The file was opened and recalculated in Apple Numbers and the results compared cell by cell with the stored values. Tabs are protected without a password, so you can unprotect a tab and read any formula. We list what we have not tested on the changelog.

Known limits

It is not accounting, bookkeeping or tax advice. It does not connect to your bank or your accounting software, so it only knows what you type. It is not a forecast you can hand to a lender as audited. If you are in serious financial difficulty, talk to a lawyer or an insolvency adviser first.

Version

Workbook 1.2.1 (October 2026). Starter 1.2. Site updated 16 October 2026. See the changelog.