Why internal growth rate matters to a first-time founder
Growth consumes cash when inventory, receivables or capacity must increase before customers pay. The internal growth rate gives a rough ceiling for expansion funded by retained profits alone. It helps founders see when a plan may require debt, new equity, better margins or a different working-capital model.
Examples of internal growth rate
A company earns £80,000 after tax, retains all of it and has average total assets of £800,000. Its return on assets is 10%, giving a simplified internal growth rate of about 11.1% using 10% divided by 90%. Faster asset growth would generally need additional financing or improved economics.
Common misunderstanding
This is not a guaranteed sales growth target or the same as sustainable growth rate. Internal growth assumes no new external finance, while sustainable growth commonly allows debt to rise in line with equity without issuing new shares. Both are model outputs whose usefulness depends on stable margins, assets and payout assumptions.
When to use it
Use it when testing a growth budget against the cash your business can generate and retain. It is most useful for established companies with meaningful profits and assets; it says little about a loss-making startup. Model cash timing directly when receivables, inventory or planned investment make the simplified ratio misleading.