Business calculations: percentages, averages and market share

About one in ten marks in Business needs calculations. They use a few simple methods again and again, so practise them until they are automatic.

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Percentages

Percentage of an amount: 15% of £240 = 0.15 × 240 = £36.
One number as a percentage of another: part ÷ whole × 100. 45 complaints out of 900 orders = 45 ÷ 900 × 100 = 5%.
Percentage change = (new − old) ÷ old × 100. Sales from £50 000 to £56 000: 6000 ÷ 50 000 × 100 = 12% increase. A negative answer is a decrease.
Interest (%) on a loan = (total repaid − amount borrowed) ÷ amount borrowed × 100.

Averages and totals

Mean = total ÷ number of values. Weekly sales of 120, 150, 90 and 140 units: (120 + 150 + 90 + 140) ÷ 4 = 125 units.
Average cost per unit = total cost ÷ number of units.
Revenue = price × quantity; total costs = fixed costs + variable costs; profit = revenue − total costs.

Market share

Market share (%) = a business's sales ÷ total market sales × 100
A firm sells £3.6 million in a market worth £24 million: 3.6 ÷ 24 × 100 = 15%.
A firm's sales can rise while its market share falls, if the whole market grows faster.

Reading data

Sales rose by 15%, but market share fell from 8% to 7.7%, because the market grew by 20%. Always say what the numbers mean for the business.
YearSales (£000)Market size (£000)
20244005000
20254606000
Worked example

Profit falls from £80 000 to £68 000. Calculate the percentage change.

  1. Change = 68 000 − 80 000 = −12 000
  2. −12 000 ÷ 80 000 × 100 = -15%

Answer: -15% (a 15% fall)

Key idea

Percentage change = (new − old) ÷ old × 100. Mean = total ÷ number of values. Market share = business sales ÷ total market sales × 100. Always explain what a figure means for the business.

Key words
Market
Where buyers and sellers come together to exchange goods and services.
Market share
Market share (%) = (one business's sales ÷ total market sales) × 100.
Percentage change
Percentage change = ((new figure − old figure) ÷ old figure) × 100.
Loan
A sum of money borrowed from a bank and repaid with interest over an agreed period.
Revenue
Revenue = price × quantity sold. Example: 400 items at £5 = £2,000.
Total costs
Total costs = fixed costs + variable costs. Total variable costs = variable cost per unit × output. Learn this.

All GCSE and International GCSE Business key terms and definitions →

Quick check

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Extra practice

2 more questions

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  1. What is 15% of £480?

    Show the answer

    Answer: 72

    15 ÷ 100 × £480 = £72.

  2. Sales rise from £60 000 to £69 900. What is the percentage increase?

    Show the answer

    Answer: 16.5 %

    (£69 900 − £60 000) ÷ £60 000 × 100 = 16.5%.

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Practise this lesson free (7 questions)All GCSE and International GCSE Business lessons

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Sources and references

Checked by the GCSE-ready editorial team, 16 October 2026. Last updated 2 October 2026. Spotted a mistake? Tell us and we will fix it.

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