Carpool Savings Calculator
Split a commute among riders and see how much each person saves on fuel every week, month and year.
How it works
Solo cost = round-trip ÷ MPG × price × days × weeks · Your share = solo ÷ riders · Saving = solo − share
When a carpool splits fuel evenly, each person’s share is the whole trip’s cost divided by the number of riders, so your saving is the part the others now cover. The first passenger delivers the biggest jump — halving your cost — and each additional rider helps less, following a one-over-N curve. This counts fuel only; real carpools often save even more by sharing tolls, parking and wear, and may unlock HOV-lane time savings.
Worked example
A 40-mile round trip at 28 mpg and $3.50/gal costs about $5.00 a day of fuel. Five days a week for 48 weeks is roughly $1,200 a year solo. Split three ways your share is about $400 — a saving of about $800 a year.
Frequently asked questions
Does the driver save the same as passengers?
If everyone splits fuel equally, yes — each person pays an equal share regardless of who drives. Many carpools rotate driving or have passengers chip in extra to offset the driver’s wear and depreciation.
Why does a fourth rider help so little?
Savings follow a one-over-N pattern: going from one to two riders halves your cost, but from three to four only trims it from a third to a quarter. Most of the benefit lands with the first one or two passengers.
What about tolls and parking?
This tool counts fuel only. Sharing tolls and parking raises the total saving further, and HOV or carpool lanes can cut commute time, which has its own value.
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This calculator is for educational purposes. Double-check important results before acting on them.