What cash runway means when income arrives in lumps
Cash runway is how many months your money lasts before your costs overtake it. Dividing cash by monthly spending works when income is steady. When $6,000 lands one month and nothing the next, timing decides whether you survive the thin month. So this calculator works month by month: the cash you hold, plus the money you expect that month, less your costs, carried forward. Why averages mislead when revenue is lumpy sets out the thinking, and a revenue forecast you can build in an afternoon applies it to a full year.
Secured money and pipeline are kept apart
Secured money is already owed or committed to you: invoices sent and not yet paid, and instalments on signed contracts. Each goes in the month you expect it to arrive, so the payment terms you set matter as much as the amount, and a due date can be worked out from the invoice date and its terms. Anything dated before the start month, such as an overdue invoice, counts in the first month.
Pipeline is proposals you have not won, each weighted by the chance you give it: a $10,000 proposal at 50% counts as $5,000. It never enters the secured balance; it gets its own line and runway, showing how much of your runway rests on unwon work.
How a signed contract becomes instalments
A signed contract is split evenly into instalments, one every month or every few months from its first. Any rounding is carried on the last instalment, so the parts add up exactly: $1,000 in three instalments is $333.33, $333.33 and $333.34. Three quarterly instalments from October 2026 land in October, January and April.
Why the first month below zero ends the runway
The runway is the number of whole months in which the closing balance stays at zero or above. The first month that closes below zero ends it, even if a later payment brings the balance back. Money due in April cannot pay March's bills, so March is when you would have to borrow, cut costs or collect something early.
A worked example
You hold $10,000 at the start of October 2026 and spend $4,000 a month. Secured payments of $6,000 are due in November and again in January. A $10,000 proposal that would pay in December has a 50% chance, so the pipeline line counts $5,000. The calculator opens with these figures, counted from the month you open it in.
| Month | Secured in | Closing balance | With pipeline |
|---|---|---|---|
| October 2026 | $0 | $6,000 | $6,000 |
| November 2026 | $6,000 | $8,000 | $8,000 |
| December 2026 | $0 | $4,000 | $9,000 |
| January 2027 | $6,000 | $6,000 | $11,000 |
| February 2027 | $0 | $2,000 | $7,000 |
| March 2027 | $0 | -$2,000 | $3,000 |
| April 2027 | $0 | -$6,000 | -$1,000 |
On secured money alone the balance holds from October to February: five months of runway, running out in March 2027. With the weighted proposal it lasts six months and runs out in April 2027. That proposal is worth a month of runway, but only if you win it.
How this differs from Secured runway on the dashboard
The RunwayDue dashboard shows a figure called Secured runway. It divides unpaid sent invoices plus the money still to come on signed contracts by your average month of collections over the last six months, all before tax. It ignores your cash and your costs, and counts contracted money whatever its date. It measures how many average months of income are already booked; this calculator asks when the cash runs out, and the two can disagree in either direction.
Frequently asked questions
How many months of runway do I need?
No single number fits, but there is a useful floor: the time it takes to turn a lead into money in the bank. If proposals take two months to sign and clients pay on net 30, a fresh lead pays in about three months, so a shorter runway means selling should already have started.
Should an overdue invoice count as secured?
Yes, in the first month: it is owed already, so the calculator counts it as arriving now. If you doubt it will arrive soon, move it to the month you expect and see how far the runway moves.
What does it mean if the runway fills the whole period shown?
The balance never went below zero in the months calculated, which means at least that long, not forever. Check how many months of costs the final balance covers.
What should go into monthly costs?
Everything that leaves in a typical month, including what you pay yourself and set aside for income tax. Enter invoices before any sales tax or GST you pass on, since that money was never yours to spend. Costs are one flat monthly figure, so spread a large annual bill across the year.
Can a month close above zero and still leave me short?
Yes. The calculator compares balances at each month end. If your costs go out on the 1st and a client pays on the 28th, you can be short for most of a month that closes in credit, so treat a month near zero as seriously as one below it.