Two Trees

Toolkit · 4 tools

Calculators

Work out percentages, compare margin and markup, find break-even units, and count or offset ISO calendar dates. Formulas, rounding and zero-denominator cases are shown.

Percentage calculator

Find percentages and percentage changes.

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Margin & markup calculator

Compare profit, margin and markup.

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Break-even calculator

Calculate units needed to cover fixed costs.

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Date & duration calculator

Count calendar days or add a day offset.

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Choose the question you are asking

The calculators show their formulas rather than hiding them behind a single answer. Work out percentages, compare margin with markup, find the units needed to cover fixed costs, or count and offset calendar dates. Inputs are currency-neutral unless the tool says otherwise.

Pick by task

  • Use the percentage calculator for a percentage of a value, a percentage change, or one number as a percent of another.
  • Use margin and markup when you need to distinguish profit as a share of selling price from profit as a share of cost.
  • Use break-even when fixed costs and contribution per unit determine how many sales are needed.
  • Use the date calculator for whole calendar days or for adding and subtracting a day offset from a valid date.

Formulas, rounding and invalid inputs

  • A zero denominator is rejected or reported as undefined; the tools do not invent a percentage.
  • Break-even rounds required units upward because a fraction of a sale does not cover the remaining fixed cost.
  • The calculators make no tax, interest, inflation, borrowing or investment assumptions. They are not financial advice.
  • Date arithmetic uses validated calendar dates and UTC ordinals to avoid daylight-saving transitions. Invalid dates are rejected.

Common questions

What is the difference between margin and markup?

Margin divides profit by selling price; markup divides profit by cost. A 50% markup is not the same as a 50% margin, and the tool shows both denominators explicitly.

Why does break-even round up?

If the exact result is 249.2 units, selling 249 leaves part of the fixed cost uncovered. The required whole-unit answer is 250.

Do dates account for time zones?

The date tool works with date-only values and UTC ordinals, not local clock times. That keeps day counts stable across daylight-saving changes.

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