Four people do not cost four times one person
Cost of living figures are usually published for an unnamed household, and readers silently assume they can multiply or divide by headcount. They cannot. Some costs are genuinely fixed at the household level, some are close to linear per person, and some jump in discrete blocks when the household crosses a threshold such as needing a second bedroom or a car. Getting the scaling wrong is the reason a relocation budget built by one person fails when the family arrives.
This article is about that scaling structure. It is not about which country is cheaper, and it does not attempt to price anything.
Three cost behaviours
- Fixed household costs. Broadly unchanged by the number of occupants: broadband, standing charges on utilities, local property or residence taxes, home insurance, and the base rent for a dwelling of a given size.
- Per person costs. Roughly linear with headcount, though usually with a discount for scale: food, clothing, personal care, public transport, mobile plans, and health cover where it is charged per head.
- Block costs. Step functions triggered by household composition. An extra bedroom, a car once school runs are involved, childcare or school fees, and a larger dwelling’s higher heating demand all appear suddenly rather than gradually.
Two further behaviours are worth naming. Some costs are negatively scaled: bulk grocery buying and family transport passes reduce the per head figure. Others are time costs converted into money, most obviously childcare, which exists so that an adult can work.
Equivalence scales, and their limits
Statisticians compare households of different sizes using equivalence scales, which convert a household into a number of equivalent adults. Two common forms exist. One assigns a weight of 1.0 to the first adult, 0.5 to each additional adult and 0.3 to each child. Another simply takes the square root of household size. Divide household spending or income by the resulting factor and you get an equivalised figure that can be compared across household types.
These scales are conventions, not measurements, and different data sources use different ones. Always check which scale a published statistic uses before comparing it with your own calculation, because the choice changes the answer materially. Note also that standard scales generally do not capture childcare or school fees, which are among the largest costs a family faces.
An illustrative worked example
The figures below are invented to demonstrate the structure, not drawn from any market. Suppose a single person and a family of four, two adults and two children, live in the same city.
| Line item | Behaviour | Single, monthly | Family of four, monthly |
|---|---|---|---|
| Rent | Block, by bedroom count | 1,100 | 1,800 |
| Utilities and broadband | Fixed plus a per person element | 150 | 260 |
| Food, clothing, personal, transport | Per person, with scale discount | 450 | 1,520 (four at 380) |
| Childcare or schooling | Block | 0 | 700 |
| Car | Block | 0 | 350 |
| Total | 1,700 | 4,630 |
Annually that is 20,400 against 55,560. The family has four times the people but 2.72 times the cost, and 1,157 per head against 1,700 for the single person. On the first equivalence scale above, the family counts as 1.0 plus 0.5 plus 0.3 plus 0.3, which is 2.1 equivalent adults, so its equivalised spending is 4,630 divided by 2.1, or about 2,205. That is 1.30 times the single person’s 1,700, which shows that the scale does not fully absorb the childcare and car blocks. The gap between the raw per head figure and the equivalised figure is the point of doing both.
Where the family and single budgets diverge most
- Housing. Price per square metre usually falls as size rises, but total rent still climbs steeply with bedroom count, and family suitable stock is concentrated in different neighbourhoods with different prices.
- Childcare. Often the largest single family line, and often means tested, subsidised, capped or rationed by waiting list. Whether it is publicly subsidised is the biggest single driver of the difference between countries for families.
- Transport. A single person can often live without a car. School and activity logistics frequently force a household into car ownership, which brings purchase or lease, insurance, fuel, parking, tax and maintenance in one block.
- Healthcare. Family cover may be a flat household premium, a per head premium, or free for dependants under a contribution based system. These three produce very different totals.
- Income side effects. Household taxation, child benefits, family allowances and tax credits can offset costs substantially, and they exist in some countries and not others. A family budget that ignores the transfer side overstates the burden.
Building your own version
- List your actual line items, not a generic basket.
- Tag each one as fixed, per person or block.
- Price the fixed items once for the dwelling you would actually rent or buy.
- Price per person items for one person, then apply a scale discount you can justify, rather than multiplying exactly.
- Add block items explicitly, with the trigger written next to each one, for example second child starts school.
- Compute three outputs: household total, per head, and equivalised. Compare all three.
- Add the transfer side separately: allowances, benefits and tax reliefs that depend on household composition.
We use three outputs rather than one because each answers a different question. The household total tells you what you must earn, the per head figure is useful for comparing lifestyles, and the equivalised figure is what lets you place yourself against published statistics. When we compare two locations for a family, we build the block costs first, because they are the items that most often change the ranking.
Childcare subsidies, family allowances, household tax treatment and housing markets vary widely by country and by city within a country. Confirm entitlements and prices with the relevant local authority, the school or provider, or a qualified professional before relying on any estimate. This article is informational only and is not financial advice.
How to Use This Guide
Every worked example on this page is illustrative. The figures are chosen to show how the calculation behaves, not to report current market rates. Costs, tax rules and eligibility criteria differ by country and change over time, so take the method from this page and put your own current figures into it. Browse the rest of our guides, or see how we source and check our comparison figures on the about page.
Information only. This article explains how costs and rules are structured. It is not financial, tax, legal or immigration advice, and it is not a recommendation to buy any property, vehicle or investment. Confirm anything that affects a decision with the relevant local authority or a qualified professional before you act on it.
Last updated: August 14, 2026