How cash flow is calculated, and why it differs from profit
Profit and cash are not the same thing, and the gap between them is what closes businesses. Profit is recorded when a sale is made; cash arrives when the invoice is actually paid. A business can report a record month, show a healthy profit on paper, and still be unable to make payroll — because the money is sitting in unpaid invoices, in stock on a shelf, or in equipment bought last quarter.
Cash flow is conventionally split three ways. Operating covers the day-to-day: money in from customers, out to suppliers and staff. Investing covers assets bought or sold. Financing covers loans raised or repaid and money put in or drawn out by owners. A business with positive operating cash flow is funding itself; one that is positive only because it borrowed is not, and the distinction is easy to lose in a single bank balance.
Timing is the heart of the problem. If customers pay in 60 days while suppliers must be paid in 30, every sale opens a 30-day hole that has to be funded from somewhere. Measured in days, that gap is the cash conversion cycle — and shortening it releases cash without requiring a single additional sale.
Worked example
A business holding 12,00,000 in cash, collecting 8,00,000 a month and paying out 10,00,000, with stock held around 45 days, customers paying in 60 and suppliers paid in 30.
| Input | Value |
|---|
| Cash on hand | 12,00,000 |
| Cash collected per month | 8,00,000 |
| Cash paid out per month | 10,00,000 |
| Net monthly burn | 2,00,000 |
| Runway | 6 months |
| DIO / DSO / DPO | 45 / 60 / 30 days |
| Cash conversion cycle | 75 days |
This business may well be reporting a profit, because revenue is booked when invoiced rather than when collected. The fix is usually timing rather than sales. Tightening collection from 60 days to 30 releases roughly one month of billings — about 8,00,000 — which extends runway from 6 months to 10 months without winning a single new customer.
How to use this calculator
- Enter opening cash as the balance actually available, excluding undrawn credit lines.
- Enter cash actually received in the period, not invoices issued — the difference between the two is the whole point.
- Enter every payment due, including loan principal and tax set aside, which are cash out even when they are not costs.
- Read net position and runway, then project the same pattern forward at least three months.
- Model your largest customer paying 30 days late to see how much headroom you genuinely have.
Frequently asked questions
How can a profitable business run out of cash?
Because profit records a sale at the moment it is invoiced, while cash records it when the customer pays. A fast-growing business often pays for materials, staff and stock well before the matching revenue is collected, so the faster it grows the more cash it consumes — even while every individual sale is profitable.
Is negative cash flow always a bad sign?
No. Negative investing cash flow usually just means the business bought equipment, and negative overall cash flow during a deliberate expansion can be entirely rational. Persistently negative operating cash flow is the one that matters, because it means the core business is not paying for itself.
How much runway should a business keep?
It depends on how predictable your revenue is and how quickly you could raise more. A common working target is enough cash to cover several months of operating costs, with more if your income is lumpy or seasonal. The number matters less than knowing it and watching it move.
What is the fastest way to improve cash flow?
Almost always collection speed, not sales. Invoice the day work is complete rather than at month end, take deposits upfront, bill long projects at milestones, and follow up the moment an invoice goes past due. Negotiating longer supplier terms works from the other side of the same gap.
Are loan repayments a cost or a cash outflow?
Interest is both — a cost in the profit statement and cash leaving the account. Principal repayment is only cash: it reduces what you owe rather than counting as an expense. This is a common reason a business shows profit while its bank balance falls.
What does the cash conversion cycle actually tell me?
How many days your money is tied up between paying for something and being paid for it. A cycle of 75 days means you fund roughly two and a half months of operations yourself. Reducing stock days or collection days, or extending payment days, all shorten it and free cash directly.
This calculator is an educational tool. Results are estimates based on the inputs you provide and do not constitute financial advice. Verify figures with your bank, broker or a qualified advisor before acting on them.