Is It Worth Driving Farther for Cheaper Gas? The Break-Even Math
How many miles you can drive to save on gas before the detour costs more than it saves – with a quick formula and table.
Updated November 3, 2026
📊 U.S. national averages · EIA week of Nov 9, 2026
A station 20 cents cheaper looks tempting – but driving there also burns fuel. Here is how to know when the detour pays off.
The formula
Saving = gallons bought × price difference
Detour cost = extra miles (round trip) ÷ MPG × price per gallon
It is worth it only if the saving is larger than the detour cost – and, ideally, worth your time.
Example
You need 12 gallons. The cheaper station is 15 cents less but 4 miles away (8 miles extra round trip). Your car gets 25 mpg and gas costs about $4.27.
- Saving: 12 × $0.15 = $1.80
- Detour cost: 8 ÷ 25 × $4.27 = $1.37
- Net: $0.43 – for perhaps 10 minutes of extra driving.
Break-even distance
Maximum extra round-trip miles before the detour costs more than it saves (25 mpg, $4.27/gal):
| Price difference | 10 gallons | 15 gallons | 20 gallons |
|---|---|---|---|
| 5¢ | 2.9 mi | 4.4 mi | 5.9 mi |
| 10¢ | 5.9 mi | 8.8 mi | 11.7 mi |
| 20¢ | 11.7 mi | 17.6 mi | 23.4 mi |
| 30¢ | 17.6 mi | 26.3 mi | 35.1 mi |
When a detour makes sense
- The cheaper station is on your route anyway – then every cent saved is a real saving.
- You are filling a large tank (pickup, SUV) and the gap is 20 cents or more.
- You are near a state line with a big tax difference (see gas tax by state).
When it does not
- Small differences (under 10 cents) more than a couple of miles away.
- Heavy traffic, which raises the fuel used for the detour.
- When your time is worth more than a dollar or two.
Run the numbers with the detour calculator on our calculators page.
Frequently asked questions
How far should I drive for cheaper gas?
At 25 mpg and about $4.27 per gallon, a 10-cent saving on 15 gallons covers about 9 extra miles round trip. Beyond that, the detour costs more than it saves.
Is it worth driving 5 miles for gas 10 cents cheaper?
Usually not: 10 extra miles round trip at 25 mpg costs about $1.70, while 10 cents on 15 gallons saves $1.50.