Understanding Car Specs: What Every Number Means
A spec sheet is a mix of numbers that predict how a car will feel, numbers that only matter on paper, and numbers that are tested under conditions you will never replicate. Here is which is which.
Performance numbers
| Number | Unit | What it tells you |
|---|---|---|
| Power | kW or hp (PS) | Ultimate capability; 1 kW = 1.36 hp |
| Torque | Nm | Low-speed shove and towing ability |
| 0–100 km/h | seconds | Comparable headline figure; rarely relevant daily |
| Top speed | km/h | Almost never relevant; often electronically limited |
| Power-to-weight | hp per tonne | Better predictor of how lively a car feels than power |
Consumption and emissions
Official consumption figures come from a standardised laboratory cycle (WLTP in Europe). They are reproducible and useful for comparing cars, but optimistic in real use — expect roughly 10–20% worse for a petrol or diesel car and considerably worse for a plug-in hybrid driven without charging.
For EVs, kWh/100 km is the equivalent figure. Quoted range divided by consumption should roughly reconcile; in winter, plan on 20–30% less.
- L/100 km — lower is better (Europe)
- kWh/100 km — the EV equivalent; 15–20 is typical
- CO₂ g/km — drives tax in many countries; proportional to fuel use
- WLTP range — a lab figure; treat 75–80% as realistic in mixed winter use
Dimensions and capacities that actually matter
Two numbers get overlooked and cause real regret: overall width including mirrors, which decides whether the car fits your garage or parking space, and turning circle, which decides how often reversing becomes a three-point turn.
Boot volume in litres is only comparable within a body style. A 500-litre estate boot is far more useful than a 500-litre SUV boot with a sloping tailgate, because usable shape matters more than volume.
| Number | Why it matters |
|---|---|
| Length | Parking spaces, garages, city manoeuvring |
| Width with mirrors | Garage doors and narrow streets — often omitted from adverts |
| Turning circle | Daily convenience; varies more than you expect |
| Boot litres (seats up / down) | Compare within the same body style only |
| Kerb weight | Predicts handling, tyre wear and consumption |
| Payload | Relevant if you carry people and luggage together |
| Towing capacity (braked) | Check against the real trailer, with a margin |
Numbers to largely ignore
- Top speed, unless you have somewhere legal to use it
- Peak power alone, without weight and torque delivery
- Boot volume compared across different body styles
- Screen size and speaker count — showroom metrics
- Nought-to-sixty differences under about half a second, which you cannot feel
Reading a spec sheet in the right order
Start with weight and power together, which tell you how the car will feel. Then torque and the revs it arrives at, which tell you how it will feel in traffic. Then real-world consumption for your mix of driving. Then the dimensions against your actual parking. Then equipment.
Done in that order, a spec sheet answers the question 'will I be happy with this car' rather than 'which car has the biggest numbers'.