# What is my variable cost?

Computes total variable cost from the cost per unit and the number of units, or from total cost minus fixed costs, with the variable cost per unit and total cost.

- Page: https://www.acalculator.org/finance/variable-cost-calculator
- JSON spec: https://www.acalculator.org/finance/variable-cost-calculator.json
- Version: be7fd440ec26

## Default answer

Example with the default inputs (Start from Cost per unit, Variable cost per unit $70.00, Units 15, Fixed costs $720.00): The total variable cost is $1,050.00.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| from | Start from | The cost of one unit and how many units, or the total cost and the fixed costs. |
| vc | Variable cost per unit | What each unit costs in materials, direct labor, commissions and other costs that rise with volume. |
| tc | Total cost | All costs for the period, fixed and variable. |
| q | Units | Units made or sold, or another measure of activity such as hours or guests. Needed when you start from the cost per unit. |
| fc | Fixed costs | Costs that stay the same as volume changes, such as rent and salaries. Needed when you start from the total cost. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| variable | Total variable cost | Variable cost per unit × units, or total cost − fixed costs. |
| unitCost | Variable cost per unit | Total variable cost ÷ units. Shown when you start from the total cost and enter units above 0. |
| totalCost | Total cost | Fixed costs + total variable cost. Shown when you start from the cost per unit and enter fixed costs. |
| average | Average total cost per unit | Total cost ÷ units, when both are known and units are above 0. |

## Method

From the cost per unit: total variable cost = variable cost per unit × units, and total cost = fixed costs + total variable cost. From the total cost: total variable cost = total cost − fixed costs, and variable cost per unit = total variable cost ÷ units. Average total cost per unit = total cost ÷ units.

## Assumptions

- Each unit costs the same, so total variable cost rises in direct proportion to the units.
- Fixed costs stay the same over the range of units you enter.
- Arithmetic is exact on the typed decimals; money shows to the cent, halves up.

## Worked examples

1. from = unit, vc = $70.00, q = 15, fc = $720.00 gives variable = $1,050.00, totalCost = $1,770.00, average = $118.00. Source: OpenStax, Principles of Managerial Accounting, 2.2 Identify and Apply Basic Cost Behavior Patterns (variable costs vary in direct proportion to activity; total cost = fixed costs + variable costs). https://openstax.org/books/principles-managerial-accounting/pages/2-2-identify-and-apply-basic-cost-behavior-patterns (Pat’s ski trip: total variable cost $1,050, total fixed cost $720).
2. from = total, tc = $8,435,000.00, fc = $1,560,000.00, q = 625 gives variable = $6,875,000.00, unitCost = $11,000.00, average = $13,496.00. Source: OpenStax, Principles of Managerial Accounting, 2.2 Identify and Apply Basic Cost Behavior Patterns (variable costs vary in direct proportion to activity; total cost = fixed costs + variable costs). https://openstax.org/books/principles-managerial-accounting/pages/2-2-identify-and-apply-basic-cost-behavior-patterns (Carolina Yachts: fixed $1,560,000, variable $6,875,000, $11,000 a boat).
3. from = total, tc = $400.00, fc = $160.00, q = 60 gives variable = $240.00, unitCost = $4.00, average = $6.67. Source: OpenStax, Principles of Economics 3e, 7.3 Costs in the Short Run (total cost = fixed cost + variable cost; average variable cost = variable cost ÷ quantity; The Clip Joint). https://openstax.org/books/principles-economics-3e/pages/7-3-costs-in-the-short-run (Table 7.9: fixed cost $160, variable cost $240, total cost $400 at 60 haircuts).
4. from = unit, vc = $3.45, q = 1,250, fc = $2,000.10 gives variable = $4,312.50, totalCost = $6,312.60, average = $5.05.
5. from = unit, vc = $12.50, q = 400 gives variable = $5,000.00. Source: OpenStax, Principles of Managerial Accounting, 2.2 Identify and Apply Basic Cost Behavior Patterns (variable costs vary in direct proportion to activity; total cost = fixed costs + variable costs). https://openstax.org/books/principles-managerial-accounting/pages/2-2-identify-and-apply-basic-cost-behavior-patterns.

## FAQ

### What is a variable cost?

A variable cost changes in direct proportion to how much a business makes or sells: materials, direct labor paid by the unit, sales commissions and shipping. Make twice as many units and the total variable cost doubles, while the cost per unit stays the same.

### How do I calculate total variable cost?

Multiply the variable cost per unit by the number of units. On Pat's ski trip, food and lift tickets cost $70 per person per day; 5 skiers for 3 days is 15 person-days, so the total variable cost is 70 × 15 = $1,050.

### How do I find variable cost from total cost?

Total cost is fixed costs plus variable costs, so subtract the fixed costs from the total cost. Carolina Yachts had $1,560,000 of fixed costs and $8,435,000 of total cost, so its variable costs were $6,875,000.

### How do I calculate variable cost per unit?

Divide the total variable cost by the number of units. Carolina Yachts built 625 boats with $6,875,000 of variable costs, so each boat had $11,000 of variable cost. Economists call this the average variable cost.

### What is the difference between fixed and variable costs?

Fixed costs, such as rent, insurance and salaries, stay the same in total when volume changes, over a normal range of activity. Variable costs rise and fall with volume. Per unit, it is the other way round: the fixed cost per unit falls as volume grows, while the variable cost per unit stays the same.

### Why does variable cost matter?

Price minus variable cost per unit is what each sale adds toward fixed costs and profit (the contribution margin). It sets the break-even point and the operating leverage of a business.

## Sources

- OpenStax, Principles of Managerial Accounting, 2.2 Identify and Apply Basic Cost Behavior Patterns: a variable cost varies in direct proportion to the level of activity, stays the same per unit, and total cost is the sum of fixed and variable costs; Pat's ski trip ($70 per person per day, total variable cost $1,050, fixed costs $720) and Carolina Yachts (625 boats, fixed $1,560,000, variable $6,875,000, $11,000 per boat). https://openstax.org/books/principles-managerial-accounting/pages/2-2-identify-and-apply-basic-cost-behavior-patterns (retrieved 2026-10-19)
- OpenStax, Principles of Economics 3e, 7.3 Costs in the Short Run: total costs are the sum of fixed plus variable costs; average variable cost is variable cost divided by the quantity produced; average total cost is total cost divided by quantity; The Clip Joint (Table 7.9: 60 haircuts, fixed cost $160, variable cost $240, total cost $400). https://openstax.org/books/principles-economics-3e/pages/7-3-costs-in-the-short-run (retrieved 2026-10-19)