Margin of Safety Calculator

Background.

Break-even analysis finds the sales level at which revenue just covers fixed and variable costs. The margin of safety asks the follow-up question every owner and lender cares about: how far above that line is the business now, and how much could sales fall before the profit is gone?

As an amount it is a plain difference, sales minus break-even sales, and it works in currency or in units sold as long as both figures use the same one. As a percentage of sales it becomes comparable between a corner café and a manufacturer a hundred times its size. A firm with a 28% margin of safety can lose a little over a quarter of its sales before it slips into a loss; one at 5% is a single bad month away.

The percentage also measures fragility. Under the usual cost-volume-profit assumptions, operating profit equals the contribution margin ratio multiplied by the margin of safety, so the thinner the cushion, the harder each lost sale lands on profit. With a 28% margin, a 10% fall in sales removes about 36% of operating profit. With an 8% margin, the same fall turns the profit into a loss.

Break-even sales are taken as an input, so work them out first, usually by dividing fixed costs by the contribution margin ratio. The page will not accept a break-even figure above sales: a business in that position has no cushion at all, only a shortfall, and the gap it needs to close is break-even sales minus actual sales.

What is margin of safety calculator?

The margin of safety is the amount by which actual or budgeted sales exceed break-even sales, the level at which total contribution margin exactly covers fixed costs and operating profit is zero. The margin of safety percentage, sometimes called the margin of safety ratio, divides that excess by sales. Both come from cost-volume-profit analysis in managerial accounting, which assumes the selling price, the variable cost per unit, total fixed costs and the product mix all hold steady across the range of sales being considered.

How to use this calculator.

1. 01Enter Actual or budgeted sales for the period you want to test: last year's revenue, this quarter's forecast or a target you are weighing up.
2. 02Enter Break-even sales for the same period and product mix. If you only know fixed costs and the contribution margin ratio, divide the first by the second: $72,000 of fixed costs at a 40% ratio gives $180,000.
3. 03Keep both figures in one unit, either both in money or both in units sold. Revenue against a unit count produces a number with no meaning.
4. 04Read the amount and the percentage. If the page rejects the break-even figure, sales are below break-even and the difference is a shortfall to close rather than a cushion.

The formula.

MOS = S − BE and MOS% = (S − BE) ÷ S × 100, where S is actual or budgeted sales and BE is break-even sales for the same period. The amount carries whatever unit the inputs use. The percentage divides by sales, not by break-even, so it reads as the share of current sales that could disappear before operating profit reaches zero; dividing by break-even instead would give 38.9% for the example below rather than 28%. In the standard linear cost-volume-profit model, operating profit = contribution margin ratio × MOS, and the degree of operating leverage equals 1 ÷ (MOS% ÷ 100). The percentage therefore also tells you how many times larger the swing in profit will be than a given swing in sales. Both inputs must be positive, and break-even may not exceed sales.

A worked example.

Frequently asked questions.

References& sources.

1. [1]OpenStax, Principles of Managerial Accounting, Cost-Volume-Profit Analysis.
2. [2]IMA, Statements on Management Accounting, cost management resources.
3. [3]BIPM, The International System of Units (SI Brochure), 9th ed., version 3.01, coherent derived units and quantity equations.