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margin of safety

How far sales can fall before the business reaches break-even, as units or as a share of current sales.

The margin of safety shows how far actual sales are above the break-even point, as a share of actual sales: margin of safety = (actual units − break-even units) ÷ actual units. It can also be computed in money. It answers a plain question: how much can sales fall before this period stops covering its fixed costs?

A margin of 25% means a quarter of the volume could disappear and the period would still break even. A negative margin means the period is already below the line, and its size says how far. Because the break-even point depends on that period's fixed costs and contribution per unit, the margin has to be computed per period: for a seasonal business, per month.

It is closely linked to operating leverage, which is roughly 1 ÷ margin of safety: the closer a period is to break-even, the more its profit swings with every change in volume. A yearly profit can therefore hide months with a negative margin of safety, which is exactly where cash problems start.

Example

In March 2026 Klasna's fixed costs were 1,038,000 UAH and each lesson left 174.48 UAH, so break-even was 1,038,000 ÷ 174.48 → 5,950 lessons. Klasna delivered 7,840:

(7,840 − 5,950) ÷ 7,840 = 24.11%.

In May, the exam peak, the margin was 35.04%. In July the line was lower, 4,820 lessons, but only 2,600 were delivered: (2,600 − 4,820) ÷ 2,600 = −85.38%, an operating loss of 391,490 UAH in a year that still ended with a profit.

Common mistakes

  • Computing it only for the year. Seasonal businesses need it per month; the annual number hides the loss months.
  • Comparing break-even points instead of distances. A lower line is not a safer month if actual volume is even lower.
  • Keeping an old line. A new hire, a step cost or a price change moves break-even; recompute before trusting the margin.
  • Ignoring the mix. When cheaper products take a bigger share, contribution per unit falls and the margin shrinks even at the same volume.

Learn it in the course