Internal growth rate estimates the maximum sales and asset growth a company can support with retained earnings and no new external financing.
The Internal Growth Rate (IGR) estimates the maximum rate at which a company can grow sales and assets using retained earnings, without issuing new debt or equity. It is a simplified financing-capacity benchmark, not a forecast that the company will actually grow at that rate.
IGR matters because growth consumes capital. More sales may require additional inventory, receivables, equipment, or other assets before the company collects the related cash. The metric tests whether internally retained profit can support that expansion under a stable set of assumptions.
Under the common end-of-period asset convention:
Where:
The denominator matters because the period’s retained earnings help fund the ending asset base. Analysts should state whether ROA uses beginning, average, or ending assets; mixing conventions can create a false difference between models.
Assume a company has:
$5.0 million10%, measured against ending assets in this simplified model40%At 4.17% growth, ending assets would be approximately $5.2083 million. Net income at 10% of ending assets would be about $520,833, and 40% retained earnings would be about $208,333. That retained amount exactly matches the modeled increase in assets.
The example explains the formula’s logic. In practice, earnings and cash may arrive after inventory, payroll, or capital spending must be funded, so a company can still need a credit line even when annual growth is below IGR.
| Driver | Effect if all else is equal | Important tradeoff |
|---|---|---|
| Higher ROA | Raises IGR | May not persist if growth requires lower-margin sales or more assets |
| Higher retention ratio | Raises IGR | Reduces dividends or other distributions to owners |
| Better asset turnover | Can raise ROA and IGR | May require tighter inventory or receivables management |
| Lower asset intensity | Reduces capital needed for each dollar of sales | Leasing or outsourcing can introduce other costs and obligations |
| Lower profitability | Reduces IGR | Revenue growth can consume financing even while earnings rise in dollars |
Increasing retention is not free financing. Shareholders give up a current distribution, and retained funds create value only if the company can reinvest them productively.
| Feature | Internal Growth Rate | Sustainable Growth Rate |
|---|---|---|
| New common equity | None | None |
| New debt | None in the simplified model | Debt may grow to preserve the target debt-to-equity relationship |
| Core profitability input | ROA | Return on Equity (ROE) |
| Main question | How fast can assets and sales grow using retained earnings alone? | How fast can they grow while maintaining leverage and payout policy? |
The Sustainable Growth Rate (SGR) is usually higher than IGR when a company uses debt, because the sustainable-growth model allows borrowing to rise with equity. It does not assume unlimited borrowing or guarantee that lenders will provide the funds.
Before using IGR in a forecast, check:
The SEC’s guide to financial statements explains the roles of the income statement, balance sheet, cash-flow statement, and statement of shareholders’ equity. U.S. public-company inputs can be checked in SEC EDGAR. An educational overview of the standard formula and the IGR-SGR distinction is available from the Corporate Finance Institute.
IGR is unreliable when the business is changing rapidly. Acquisitions, divestitures, idle capacity, large one-time capital projects, volatile margins, negative earnings, or major working-capital swings can break its assumptions. Reported ROA may also be distorted by asset write-downs, acquisitions, leases, or a large cash balance.
The metric also does not measure whether growth creates value. A company can finance growth internally and still earn less than its cost of capital.
This material is educational and is not accounting, financing, or investment advice.