Performance Management · Planning and operational variances

Market Size and Market Share Variance in ACCA PM

Updated 11 October 2026 · Fact-checked

Market size and market share variances split the sales volume variance into two causes. The market size variance shows the effect of the whole market being bigger or smaller than planned. The market share variance shows the effect of the company winning more or less of the market. Both use standard contribution per unit.

Understand Sales Variances: Market Size and Market Share

The sales volume variance tells you that you sold more or fewer units than budget. It does not tell you why. Two things could have happened. The whole market may have grown or shrunk, or your business may have won or lost customers compared with rivals.

The market size variance measures the first cause. It asks: if our share had stayed at the budgeted level, what would the change in market size have done to profit? Management usually cannot control the size of the market, so this is often treated as a planning-type, uncontrollable variance.

The market share variance measures the second cause. It asks: given the market size that actually happened, what was the effect of our share being higher or lower than planned? This is the operational part, because sales, pricing and marketing teams can influence share.

The two variances always add up to the sales volume variance. Use this as a check. Both are valued at the standard contribution per unit under marginal costing, or standard profit per unit under absorption costing. Use whichever the question gives for the sales volume variance.

A favourable (F) variance means more profit than budget. An adverse (A) variance means less.

Key rules to remember

Market size variance: (Actual market size − Budgeted market size) × Budgeted market share % × Standard contribution per unit; Uses budgeted share, so it isolates the market effect. Positive result is F, negative is A. Market size must be in the same units as sales.
Market share variance: (Actual market share % − Budgeted market share %) × Actual market size × Standard contribution per unit; Uses actual market size, so it isolates the effect of share. Positive result is F, negative is A.
Actual market share: Actual market share % = Actual sales units ÷ Actual market size; Use this when the question gives sales and market size but not the share.
Check total: Market size variance + Market share variance = Sales volume variance = (Actual sales units − Budgeted sales units) × Standard contribution per unit; If your two answers do not add up to this, one of them is wrong.

How to solve Sales Variances: Market Size and Market Share questions

Follow the same order each time. It keeps the two variances separate and gives you a built-in check.

1Find the budgeted sales units and the budgeted market share. Budgeted share = budgeted sales ÷ budgeted market size, if not given.
2Find the actual sales units and actual market size. Work out actual market share = actual sales ÷ actual market size.
3Identify the standard contribution per unit (or profit per unit under absorption costing). Do not use selling price.
4Calculate the market size variance: change in market size × budgeted share × standard contribution. Mark it F or A.
5Calculate the market share variance: change in share % × actual market size × standard contribution. Mark it F or A.
6Calculate the sales volume variance directly from units and check that the two variances add up to it.
7Interpret in a sentence each: say what happened to the market and to your share, and whether management could control it.

Quickest way: Units shortcut

When to use it: Use when the question gives units, as most do, and you want fewer chances of arithmetic slips.

Work out the budgeted share % from budget sales ÷ budget market size.
Market-size effect in units = (Actual market − Budget market) × budgeted share %.
Share effect in units = Actual sales − (Actual market × budgeted share %).
Check: the two unit effects add up to actual sales − budgeted sales.
Multiply each unit effect by standard contribution per unit and label F or A.

Common mistakes in Sales Variances: Market Size and Market Share

Using actual share in the market size variance, or budgeted market size in the market share variance.
The two formulas look alike and students mix up which figure is held constant.
Fix: Remember the rule: market size variance holds share at budget; market share variance holds market size at actual.
Valuing the variances at selling price or revenue per unit.
Students think of sales variances as revenue variances.
Fix: Use standard contribution per unit (marginal costing) or standard profit per unit (absorption costing), as the sales volume variance does.
Getting the sign wrong, for example calling a fall in market size favourable.
Students focus on the number rather than the direction of change.
Fix: A smaller market than budget gives an adverse market size variance. A higher share than budget gives a favourable share variance. Check the sign against the sales volume variance.
Mixing units and percentages, such as using 11 instead of 0.11.
Shares are quoted as percentages and the calculator needs decimals.
Fix: Convert every percentage to a decimal before multiplying and keep market size and sales in the same units.
Confusing market size and share variances with sales mix and quantity variances.
Both split a sales volume variance into two parts.
Fix: Market size and share split by cause across the whole market for one product line. Mix and quantity split by product when several products are sold. Read what data the question gives.
Giving numbers without comment.
Students run out of time or forget that the written part carries marks.
Fix: Add one line for each variance. State the cause, whether it was controllable, and who is responsible.

Worked examples

Example 1

A company budgeted a market of 500,000 units and a 10% share, giving budgeted sales of 50,000 units. Standard contribution is $12 per unit. Actual market size was 450,000 units and actual sales were 49,500 units. Calculate the market size, market share and sales volume variances.

Show the solution

Budgeted share = 10%. Actual share = 49,500 ÷ 450,000 = 11%.
Market size variance = (450,000 − 500,000) × 10% × $12 = −5,000 units × $12 = $60,000 A.
Market share variance = (11% − 10%) × 450,000 × $12 = 4,500 units × $12 = $54,000 F.
Sales volume variance = (49,500 − 50,000) × $12 = $6,000 A.
Check: $60,000 A + $54,000 F = $6,000 A. This matches.

Answer: Market size variance $60,000 A; market share variance $54,000 F; sales volume variance $6,000 A. The market shrank, which management could not control, but the company won a larger share and almost offset the loss.

Example 2

Budgeted market size was 2,000,000 units and budgeted share 5%. Standard contribution is $8 per unit. Actual market size was 2,200,000 units and the company sold 99,000 units. Calculate the variances and comment.

Show the solution

Budgeted sales = 2,000,000 × 5% = 100,000 units. Actual share = 99,000 ÷ 2,200,000 = 4.5%.
Market size variance = (2,200,000 − 2,000,000) × 5% × $8 = 10,000 units × $8 = $80,000 F.
Market share variance = (4.5% − 5%) × 2,200,000 × $8 = −11,000 units × $8 = $88,000 A.
Sales volume variance = (99,000 − 100,000) × $8 = $8,000 A.
Check: $80,000 F + $88,000 A = $8,000 A. This matches.
Comment: the market grew by 10%, but the company did not keep up and lost share. The overall adverse variance hides a serious operational problem.

Answer: Market size variance $80,000 F; market share variance $88,000 A; sales volume variance $8,000 A. The market grew but the company's share fell, so the share variance points to poor sales performance.

Exam tips

Always do the check against the sales volume variance. It takes ten seconds and catches most errors.
Write the unit effects first, then multiply by contribution. Markers can award method marks for the units.
In objective test questions, watch for distractors that use selling price, or swap actual and budget figures. Check which figure the question wants held constant.
In written parts, link market size to planning (uncontrollable) and market share to operational performance, but say that this depends on the scenario.
If the question gives profit per unit under absorption costing, use that figure consistently for all three variances.

Practice questions from Planning and operational variances

Sales Variances: Market Size and Market Share: frequently asked questions

Is the market size variance a planning variance?

It is usually treated as a planning-type variance because the size of the market is outside management's control. The market share variance is the operational part. Read the question, as the wording may ask you to comment differently.

Why do the two variances add up to the sales volume variance?

They split the same change in units into two steps. The first step changes the market size at budgeted share. The second changes share at the actual market size. Together they move you from budgeted sales to actual sales.

Do I use contribution or selling price?

Use standard contribution per unit under marginal costing. Under absorption costing use standard profit per unit. Never use selling price, because the variance measures the effect on profit.

How is this different from sales mix and quantity variances?

Mix and quantity variances split the sales volume variance when several products are sold. Market size and share variances split it by cause: the market as a whole against your own performance within it.