The constraint that produces the formula
Growth consumes cash. More sales need more inventory, more receivables and eventually more plant, and those assets have to be paid for. A company has exactly three ways to pay: retain profit, borrow, or sell shares. The sustainable growth rate answers what happens when you rule out the third and require the second to stay in fixed proportion to the first.
Under those constraints the arithmetic is forced. Equity at the end of the year is equity at the start plus retained profit, so equity grows by net income × b ÷ equity, which is ROE × b. If the debt-to-equity ratio is to stay put, debt must grow at the same rate. Assets are debt plus equity, so assets grow at that rate too. And if asset turnover is unchanged, sales grow at that same rate. One number therefore governs the whole balance sheet: SGR = ROE × b.
Robert Higgins built this into a planning framework in the 1970s, and its value is not that it forecasts anything — it does not — but that it makes an inconsistency visible. A management team forecasting 18% sales growth while paying out 60% of a 15% ROE is planning something arithmetically impossible without new capital or rising leverage. The model does not say which of those they should do; it says they must do one of them.
The two rates, and which equity to use
The retention ratio is one minus the payout ratio. Include buybacks in the payout: repurchasing stock consumes retained profit exactly as a dividend does, and a company running a large buyback while reporting a low dividend payout is retaining far less than its dividend ratio suggests.
The internal growth rate is the stricter cousin. It rules out new borrowing as well as new equity, so growth is limited by what retained profit alone can fund relative to the whole asset base. Its formula, ROA·b ÷ (1 − ROA·b), has a denominator because retained profit adds to assets during the year, so the growth is measured against a base that is itself growing. The internal growth rate is always lower than the sustainable growth rate for a company with any debt at all, because IGR forgoes the borrowing that SGR permits.
Which equity figure? This matters more than it looks. If ROE is calculated on beginning equity, then SGR = ROE × b is exact. If ROE uses ending equity — the more common convention in published data — the consistent version is SGR = ROE·b ÷ (1 − ROE·b), which is always the larger of the two. At a 15% ROE and 70% retention, the difference is 10.50% against 11.73%: over a decade that is a compounding gap of about 12%. This calculator reports both and labels which is which, so you can match whichever convention your ROE came from. The return on equity calculator lets you set that basis explicitly.
Worked example: a 15% ROE with a 30% payout
Take the defaults, in millions: net income $480, dividends and buybacks $144, common equity $3,200, total assets $8,000.
- Payout ratio. 144 ÷ 480 = 30.0%.
- Retention ratio. 1 − 0.30 = 0.70.
- Return on equity. 480 ÷ 3,200 = 15.0%.
- Sustainable growth rate. 15.0 × 0.70 = 10.5%.
- Check it against the balance sheet. Retained profit is 480 × 0.70 = $336M, and 336 ÷ 3,200 = 10.5%. Equity grows from $3,200 to $3,536. To keep debt at its current $4,800 (8,000 − 3,200) times the same proportion, debt must rise by 10.5% too, to $5,304. Assets then reach 3,536 + 5,304 = $8,840, which is exactly 8,000 × 1.105.
- Internal growth rate. ROA is 480 ÷ 8,000 = 6.0%, so ROA × b = 0.042 and IGR = 0.042 ÷ 0.958 = 4.3841%. Without new borrowing, the same company can grow at only about four percent.
- Beginning-equity form. 0.105 ÷ (1 − 0.105) = 11.7318%, the figure to use if your 15% ROE was computed on year-end equity.
Step 5 is the point of the whole exercise. Every number on the balance sheet grows by the same 10.5%, and nothing about the capital structure changes. That is what "sustainable" means here — not desirable, not likely, just self-consistent.
What to do when actual growth differs from SGR
Growing faster than SGR. The gap has to be funded. The four levers are: raise the payout less (increase b), improve margins or asset turnover (increase ROE through operations), take on more leverage (increase ROE through the equity multiplier), or issue equity. Each has a cost, and the DuPont decomposition is the right tool for deciding which of the first three is actually available — a company already at four turns of leverage cannot borrow its way to growth again.
Growing slower than SGR. The company is accumulating capital it is not using. That shows up as a rising cash balance or a falling debt ratio, and it drags ROE down over time because the equity base grows while profit does not. The standard responses are to raise the payout, buy back stock, or find acquisitions. A firm persistently below its SGR with no plan for the surplus is a candidate for pressure from shareholders.
The model assumes constant margins and constant asset turnover. Both are strong assumptions. A company that can grow sales without proportionally growing assets — because it has spare capacity, or because it is shifting toward an asset-light model — can exceed its calculated SGR for years without any external finance. Treat SGR as a consistency check on a plan, not as a ceiling on reality.
Watch the direction of the leverage assumption. SGR permits debt to grow at the same rate as equity, which keeps the ratio constant but grows the absolute debt every year. If interest rates or covenant headroom will not support that, check the plan against interest coverage and net debt to EBITDA before relying on the number.
Sustainable growth rate by ROE and retention
| ROE | b = 0.3 (70% payout) | b = 0.5 | b = 0.6 | b = 0.7 | b = 1.0 (no dividend) |
|---|---|---|---|---|---|
| 8% | 2.4% | 4.0% | 4.8% | 5.6% | 8.0% |
| 10% | 3.0% | 5.0% | 6.0% | 7.0% | 10.0% |
| 12% | 3.6% | 6.0% | 7.2% | 8.4% | 12.0% |
| 15% | 4.5% | 7.5% | 9.0% | 10.5% | 15.0% |
| 18% | 5.4% | 9.0% | 10.8% | 12.6% | 18.0% |
| 20% | 6.0% | 10.0% | 12.0% | 14.0% | 20.0% |
The right-hand column is the ceiling: a company retaining every dollar of profit grows equity at exactly its ROE. No dividend policy can push sustainable growth above return on equity.
Assumptions and limits worth stating out loud
- Constant net margin. The model holds profitability fixed. Growth that comes with price competition or a worse customer mix breaks it immediately.
- Constant asset turnover. Sales are assumed to need assets in the same proportion as today. A company with spare capacity can grow well beyond its SGR until the slack runs out.
- Constant leverage. Debt is assumed to grow with equity. Whether lenders will supply it at the same rate is a separate question the model cannot answer.
- No new share issuance. That is the defining constraint. An equity raise makes the whole calculation moot for that year.
- Buybacks count as payout. Omitting them overstates the retention ratio and therefore the sustainable growth rate.
- Loss-making years break it. With negative net income the retention ratio is not meaningful and the formula produces a number with no interpretation.
Where SGR fits in financial planning and valuation
In planning, SGR is a reconciliation device. Put the sales forecast, the dividend policy and the target capital structure on one page, and the model tells you whether all three can be true at once. Most of the value comes from the argument the gap forces, not the number itself.
In valuation, the same product ROE × b appears as the growth rate in a constant-growth dividend model and in the justified price-to-book ratio. That is not a coincidence: both ask what growth a firm can finance out of retained profit. A DCF that assumes long-run growth well above the company's sustainable rate is implicitly assuming perpetual external financing, and should say so.
Two related measures are worth having alongside it. ROE is the raw input, and the DuPont breakdown tells you which of margin, turnover and leverage is driving it. On the operating side, the EVA question is more fundamental than the growth question: growth financed at a return below the cost of capital destroys value however sustainable it is.
Key terms
- Retention ratio (plowback)
- The fraction of net income kept in the business rather than paid out: b = 1 − payout ratio.
- Internal growth rate
- The growth rate financeable from retained profit alone, with no new debt and no new equity: ROA·b ÷ (1 − ROA·b).
- Equity multiplier
- Total assets divided by equity. It is the leverage term in the DuPont decomposition, and holding it constant is what makes SGR "sustainable".