Cost behavior: fixed, variable and step costs

Cost behavior is how a cost reacts to volume. To find it, put each cost column next to lessons_delivered and watch it month by month.

At Klasna three columns move with lessons: tutor payouts (a set amount per lesson), payment fees (2.5% of what families pay) and video + AI (billed by usage). These are variable costs. In December 5,192 lessons cost 2,066,416 UAH in payouts; in May 9,620 lessons cost 3,867,240.

Variable costs compare best per lesson: add the three variable columns for a month and divide by lessons delivered. November 2025: 2,495,460 + 96,558 + 194,370 = 2,786,388 UAH; 2,786,388 / 6,270 = 444.40 UAH per lesson. Over the year this number stays between 442 and 450, while the monthly totals swing by a factor of three. That stability is the signature of a variable cost.

Leave salaries, office, coordinators and marketing out: they do not grow with each lesson.

A step cost stays flat over a range of volume and then jumps by a whole block at once.

Klasna's support coordinators are the clearest case. Each costs 38,000 UAH a month and looks after up to 400 active learners, and Klasna adds one for every started 400. So the number of coordinators is learners ÷ 400, rounded up:

• up to 1,200 learners: 3 coordinators, 114,000 UAH;
• 1,201 to 1,600: 4 coordinators, 152,000 UAH;
• up to 800: 2 coordinators, 76,000 UAH.

In the year of data, February (1,010) and March (1,120) stay at three. April (1,260) is the first month past 1,200, and the column jumps to 152,000. May (1,300) keeps four. In summer, with 520 to 760 learners, seasonal contracts let Klasna go down to two.

To find a step, look for the first period that crosses the threshold, not the period where the cost is highest.

It is tempting to turn a step cost into a per-unit cost: 38,000 UAH per coordinator, 400 learners per coordinator, so about 95 UAH per learner. That number describes an average, not how the cost behaves.

Watch what really happens at Klasna. With 801 to 1,200 active learners, coordinators cost 114,000 UAH, whether there are 850 learners or 1,190. Learner 1,201 does not add 95 UAH; they add a whole coordinator, 38,000 at once. The next 399 learners add nothing.

This matters in two directions:

• Just below a threshold, growth is cheap: hundreds of extra learners cost no extra coordinator.
• Just above a threshold, a few extra learners are expensive: one learner can raise monthly costs by 38,000 UAH.

When you plan volume near a threshold, check which side of it you land on. A smooth per-learner average hides the jump that will actually hit the budget.

Marketing at Klasna rises in spring and falls in summer, just like lessons, so it is tempting to call it variable. Run the test instead: does one more lesson add marketing spend? No. The budget is set each month: 320,000 UAH for April and May, because that is exam season, and 150,000 in July, because Leo cut it.

So within a month marketing behaves as fixed: it does not react to lessons. It is a discretionary fixed cost, a cost that someone decides on period by period. Two consequences:

• For break-even it counts as a fixed cost of its month, next to salaries and the office.
• Fixed does not mean unavoidable. Next month's budget can be different by a decision, without any change in volume.

A cost moving in the same direction as volume is not proof that it is variable. Ask what causes the movement: lessons, or a choice.

Fixed costs are fixed only within a range of volume and a period of time, called the relevant range. Inside it, one more lesson or one more learner changes nothing. Outside it, the cost moves.

Klasna today has about 1,000 to 1,300 active learners in the busy months. If Leo doubles that to 2,600:

• coordinators: 2,600 / 400 = 6.5, rounded up to 7, so 266,000 UAH a month instead of 114,000;
• the team of 540,000 a month would probably need more people;
• the office and tools might need to grow too.

Time matters as well. Over a longer period everything moves for reasons unrelated to volume: a pay rise next year changes the 540,000 even if lessons stay the same.

That is why coordinators are a helpful picture of all fixed costs: stretch the range far enough, and every fixed cost turns into a step. Plans that double volume need a new cost base, not today's fixed costs.

Fixed and variable describe one thing only: how a cost reacts when volume changes. A fixed cost does not change when Klasna delivers one more lesson. That label says nothing about whether the cost can be cut.

Klasna's year shows three speeds of change:

• Marketing changes fastest: 320,000 UAH in April and May, 150,000 in July, by a decision.
• Coordinators change with the season: four in spring, two in summer, thanks to seasonal contracts.
• Team salaries change slowly: 540,000 every month this year, but a pay rise or a new hire next year will move them.

So when someone says "we can't touch fixed costs", they are mixing two questions. "Does it react to volume?" decides whether a cost goes into contribution margin. "Can we change it, and how fast?" decides what management can do about it. Keep the two apart, and use the first one for break-even.

Sorting costs by behavior is the groundwork for break-even. Klasna's monthly table has seven cost columns, and each lands in one box:

The three variable costs are each driven by lessons in their own way: per lesson, per hryvnia paid, per minute used. For break-even, the step cost and marketing are counted with the fixed costs of their month, because neither grows with one more lesson. Over the year that gives variable costs of 31,932,876.28 UAH and fixed costs of 11,668,000, so variable costs are about 73% of all spending.

For break-even, Klasna splits each month into two piles:

• variable costs: tutor payouts, payment fees, video + AI;
• fixed costs of the month: everything else, that is team salaries, office and tools, support coordinators and marketing.

Coordinators are a step cost and marketing is a monthly decision, but neither grows with one more lesson, so both go into the fixed pile of their month.

July 2026, the quietest month: coordinators 76,000 (two of them for 520 learners) + salaries 540,000 + office and tools 84,000 + marketing 150,000 = 850,000 UAH. In April the same pile is 1,096,000, because there are four coordinators and the spring marketing budget.

So "fixed" does not mean "the same number every month". It means the number does not depend on how many lessons happen inside that month. Over the whole year the fixed pile adds up to 11,668,000 UAH, against 31,932,876.28 of variable costs.