Carpooling Calculator
Work out how much each person should chip in for a shared car journey — and how much everyone saves versus driving it alone.
Fuel cost per person
£1.75
- Total fuel cost
- £7.00
- People sharing
- 4
- Each person saves vs driving alone
- £5.25
- Fuel used (litres)
- 7.57
The whole trip’s fuel cost is worked out from distance, fuel economy and pump price (all converted internally with exact NIST factors), then split equally across everyone in the car including the driver. Cost per person = total fuel cost ÷ people; the saving is what each rider avoids paying by not driving the trip alone.
How to use this calculator
Enter the total distance of the trip — there and back if it’s a return journey — and pick miles or kilometres. Set how many people are sharing the ride (count the driver too). Then enter the car’s fuel economy in whatever unit you have (US mpg, UK mpg, L/100km or km/L) and the pump price in the unit it’s sold in (per US gallon, per Imperial gallon or per litre). You can mix units freely — the calculator converts everything internally. The result is the fuel cost each person should pay, plus what everyone saves compared with driving alone.
How the calculation works
First the whole trip’s fuel cost is calculated: distance is converted to kilometres, fuel economy to litres per kilometre, and price to price per litre, all with exact NIST factors (1 mile = 1.609344 km, 1 US gallon = 3.785411784 L, 1 Imperial gallon = 4.54609 L). Fuel used = distance × consumption; total cost = fuel used × price per litre. That total is then divided equally across everyone in the car, driver included, to give the cost per person. The saving shown is the total cost minus one person’s share — i.e. what each rider avoids paying by sharing the drive rather than making the trip solo.
Worked example
Four people share a 60-mile round trip in a car doing 30 mpg-US, with petrol at $3.50 per US gallon. Fuel used = 60 ÷ 30 = 2 US gallons, so total cost = 2 × $3.50 = $7.00. Split four ways, that’s $1.75 each, and every rider saves $7.00 − $1.75 = $5.25 versus driving the whole trip alone. A UK example: two people share a 100 km trip at 8 L/100km with diesel at £1.60 per litre — fuel used = 8 L, total = £12.80, so £6.40 each, saving £6.40 apiece.
Frequently asked questions
Does the split include the driver?
Yes — by default the total fuel cost is divided equally across everyone in the car, driver included, because the driver’s fuel is part of the same trip cost. If your group prefers the driver to ride free (a common thank-you for driving), divide the total by the number of passengers instead of the total headcount: set the “people sharing” field to the number of passengers only.
Should I enter one-way or round-trip distance?
Enter the total distance actually driven. For a daily commute where everyone travels there and back together, that’s twice the one-way distance — a 20-mile-each-way commute is 40 miles total. If passengers are only in the car one way (for example, a lift to the airport), enter just the distance they share.
Does this include tolls, parking or wear and tear?
No — it splits fuel cost only. Tolls and parking are easy to add on top: divide those separately by the same number of people and add to each share. Vehicle wear, tyres, insurance and depreciation are real costs of driving too; some carpools add a small per-mile amount to cover them, similar to a mileage allowance, but that’s a group decision rather than a fuel calculation.
How do I handle passengers who only ride part of the way?
The simplest fair approach is to split each leg of the journey by the number of people in the car for that leg, then add up each person’s shares. This calculator assumes everyone shares the whole trip, so for uneven journeys run it once per leg with the right headcount and distance, then total the per-person amounts.
What fuel economy figure should I use?
Use your car’s real-world average if you know it — the trip computer’s long-term figure is more accurate than the brochure number. As a rough guide, a mid-size petrol car does about 25–35 mpg-US (30–42 mpg-UK, or 7–9 L/100km). A carrying a full load of passengers uses a little more fuel than when empty, but the difference is usually small compared with the saving from sharing.
Is carpooling actually cheaper than driving alone?
For the fuel portion, yes — sharing always divides the same fuel cost across more people, so each person pays less the more riders there are. With four people, everyone pays a quarter of the fuel. The trade-off is convenience and detours to pick people up, which add a little distance; enter the real total distance including detours to keep the estimate honest.