Get paid sooner
When it may fit: Customers pay late.
Evidence needed: Prepayment, deposits or card terms.
Trade-off: Customers may resist.
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How to Estimate Working Capital Requirements
Working capital is the cash tied up between paying for what you sell and being paid for it. In some businesses it is small. In others it is larger than the startup costs.
1. The business problem
How much cash is locked up between paying suppliers and collecting from customers?
A business that pays suppliers on delivery and collects from customers weeks later has to finance the gap. The faster it grows, the larger the gap becomes, which is why growing businesses so often run short of cash.
Simple startup models usually leave this out. That is reasonable for a business that is paid in advance, and dangerous for one that is not.
2. What the evidence can reveal
Working capital depends on timing:
- Calculated How long customers take to pay, in days.
- Calculated How far ahead inventory or materials are bought, and how long suppliers give to pay.
- Calculated Monthly sales, which determine how much cash is tied up for a given delay.
- Information gap Deposits, prepayments and seasonal swings in sales and purchasing.
The amount tied up grows with sales, so a business that doubles its sales doubles its working capital.
3. Investigate the problem
The experience below does not model working-capital timing. Its method note says so, and Calculated that is acceptable for the sample, a meal-prep service that can be paid before it delivers. Illustrative At maturity the sample sells about 600 units at $62, or $37,200 a month. If customers pay when they order, little cash is tied up.
Illustrative Change one assumption and the answer changes sharply. Suppose the same business sold to offices that pay 45 days after delivery. Receivables would be about 1.5 months of sales, about $55,800 ($37,200 times 1.5), nearly twice the $30,000 reserve and more than the $45,000 startup investment. The business could be profitable on paper and short of cash in practice.
Hypothesis Any founder who sells to businesses, buys inventory ahead or has long supplier lead times should expect working capital to matter. Information gap The tool cannot see these timing effects, which is a limit worth knowing about. The fix is to add them yourself: estimate days to collect, days of inventory and days to pay suppliers, and add the cash tied up to the need.
4. Explore the interactive experience
Investigate it yourself.
Business Idea Investigator: a guided investigator that separates evidence from assumptions, a startup financial simulator with three cases, scripted answers from APIS, and a printable preliminary assessment, all running on what you type.
The experience below starts with a sample idea. Replace it with your own, or clear it. Nothing you type leaves your browser, and APIS supplies no market data here.
- In Startup economics, find the monthly sales at maturity (price times volume).
- Multiply by 1.5 for a 45-day payment delay. Compare that with your cash reserve.
- Ask APIS “How long does my cash last?” and note what it says the model leaves out.
5. Evaluate possible solutions
Working-capital pressure can be reduced from both sides of the gap.
6. What leadership should do next
Questions to answer
- How long do customers take to pay?
- How far ahead do I buy, and how long do suppliers wait?
- How much cash is tied up at current sales?
- How much more at double the sales?
Data to gather
- Customer payment terms
- Supplier terms
- Inventory plans
- A monthly sales forecast
Steps to take
- Estimate days to collect and to pay.
- Compute cash tied up.
- Add it to the funding need.
- Review as sales grow.
7. Engage Two Pillars
Turn Your Business Idea Into a Structured Plan
Two Pillars can help founders evaluate business concepts, research markets, build financial models, plan operations and coordinate the professional guidance a new business needs. A good first step is a working-capital estimate that adds payment timing to your startup cash model.
Sources and data notes
- The organization, its figures, and every number in this article and its interactive experience are synthetic and illustrative. They are not real data, a benchmark, or a forecast.
- Reviewed October 2026. This article describes an approach to investigation. It does not replace review by qualified professionals, and it is not legal, tax or financial advice.