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Commute cost calculator
Put your miles per day, mpg, gas price and days per month in: a 36-mile daily drive at 30 mpg and $3.60 a gallon costs $4.32 a day — $86.40 a month over 20 days, $1036.80 a year.
★ EVERYDAY · COMMUTE · DRIVING
Commute Cost Calculator: $86.40 a Month, 36 Miles a Day
On the defaults — a 36-mile daily drive at 30 mpg and $3.60 a gallon over 20 days — the commute cost is $86.40 a month, $4.32 a day, 1.2 gallons a day, and $1036.80 a year. This is the commute cost tool: divide the miles by the mpg for the gallons, multiply by the gas price for the day, and multiply by the days for the month — a commute guessed by the tank tells you nothing until the miles and the mpg behind it are known.
What does $86.40 a month, $4.32 a day mean?
It means a driver covering 36 miles a day in a car that manages 30 miles a gallon burns 1.2 gallons a day, and at $3.60 a gallon that fuel costs $4.32 a day, $86.40 across a 20-day month, and $1036.80 across a year of identical months. The miles set the gallons, the mpg sets how far each gallon goes, the price sets only the money, and the days set only the month: the same 1.2 gallons cost $5.04 a day where gas is $4.20 a gallon, while the fuel itself never changes. The only judgement is the mpg — a car’s rated mpg is a laboratory figure, and a car in traffic, in winter, or with a roof box drinks more than its rating promises.
Output · formula · meaning
| Output | Formula | What it means |
|---|---|---|
| Gallons per day | miles ÷ mpg | 1.2 gallons — 36 ÷ 30. |
| Cost per day | gallons × price | $4.32 — 1.2 × $3.60. |
| Cost per month | daily cost × days | $86.40 — $4.32 × 20. |
| Cost per year | monthly cost × 12 | $1036.80 — $86.40 × 12. |
Three things to check before you trust the number
First, check the miles honestly: 36 miles must be the round trip, not one way — a 18-mile one-way commute doubled is the day, and a one-way figure fed to the calculator halves the real month. Second, check the mpg against a real tank, not the rating: divide miles driven by gallons filled over two or three tanks, because traffic, cold starts, and short trips all pull the real mpg below the brochure figure, and the calculator trusts the mpg you enter. Third, check the days against the real month: 20 days suits a weekday commuter, while a part-time week, holidays, and remote days all cut the month — a month of 20 days counted on a 15-day reality overstates the bill by a third.
Worked example
36 miles a day, 30 mpg, $3.60 a gallon, 20 days a month. Gallons: 36 ÷ 30 = 1.2 a day. Daily cost: 1.2 × $3.60 = $4.32. Monthly cost: $4.32 × 20 = $86.40. Yearly cost: $86.40 × 12 = $1036.80. In practice that means a 36-mile daily commute costs about four dollars and thirty cents a day in fuel — the number to compare against a transit pass, and the yearly figure to use when a thriftier car promises to pay for itself.
Every branch, checked
With 50 miles a day instead of 36, the day uses 1.67 gallons — $6.01 a day, $120.20 a month, $1442.40 a year. With 20 mpg instead of 30, the day uses 1.8 gallons — $6.48 a day, $129.60 a month, $1555.20 a year. With gas at $4.20 a gallon instead of $3.60, the gallons stay 1.2 but the day costs $5.04 — $100.80 a month, $1209.60 a year. With 15 days a month instead of 20, the day stays $4.32 but the month falls to $64.80, and the year to $777.60.
The reverses, worked backwards
The miles behind $86.40 are 36 a day: at 24 miles the month is $57.60 (0.8 gallons a day, $2.88 a day, $691.20 a year); at 48 miles it is $115.20 (1.6 gallons a day, $5.76 a day, $1382.40 a year). The mpg behind $86.40 is 30: at 20 mpg the month is $129.60 (1.8 gallons a day, $6.48 a day, $1555.20 a year); at 40 mpg it is $64.80 (0.9 gallons a day, $3.24 a day, $777.60 a year). The price behind $86.40 is $3.60: at $3.00 the month is $72.00 (1.2 gallons a day, $3.60 a day, $864.00 a year); at $4.20 it is $100.80 (1.2 gallons a day, $5.04 a day, $1209.60 a year) — the price never touches the gallons, only the money.
What the defaults assume
The defaults assume a 36-mile daily drive at a true 30 mpg and $3.60 a gallon, driven 20 days a month all year. They do not assume tolls, parking, wear, insurance, or a car that drinks more in traffic or winter — a tolled route, a paid garage, and a cold-start short trip all add costs the fuel figure never sees, so treat $86.40 as the fuel month, not the whole cost of commuting.
Who uses this
- A commuter comparing driving with transit: the $86.40 fuel month is the line to set against the pass price.
- A job-seeker weighing a farther office: the $4.32 day is the line for each extra mile of commute.
- A household budgeting the car: the $1036.80 year off the calculator is the fuel budget line, not a guess.
- A car shopper choosing a thriftier model: the mpg gap in the month is the payback figure for the dearer car.
Accuracy & limitations
The arithmetic is exact for the inputs entered; the judgement is the miles, the true mpg, and the price. Real cars vary with traffic, weather, load, and driving style, and real months vary with holidays and remote days — so treat $86.40 as the planning fuel month for a 36-mile drive at a true 30 mpg and $3.60 a gallon, and check it against a metered month of fill-ups before quoting it to anyone else.
Cite this calculator
Bright Side Kit, “Commute Cost Calculator: $86.40 a Month, 36 Miles a Day”, https://brightoolbox.com/commute-cost-calculator/, accessed 3 November 2026. Students and researchers: cite the calculator name, the page URL and the date you used it, and quote the defaults (36 miles a day, 30 mpg, $3.60 a gallon, 20 days a month) so the result can be checked.
Frequently asked questions
How much does a 36-mile commute cost a month?
$86.40 in fuel on the defaults: 36 ÷ 30 = 1.2 gallons a day, 1.2 × $3.60 = $4.32 a day, and $4.32 × 20 days = $86.40, or $1036.80 across a year of identical months.
Should I enter one-way or round-trip miles?
Round-trip: the day is the drive there and back. An 18-mile one-way commute is 36 miles a day, and a one-way figure fed to the calculator halves the real month.
Why is my real mpg lower than the rating?
Because the rating is measured in a laboratory cycle, while traffic, cold starts, short trips, air conditioning, and a roof box all drink extra fuel. Measure the true mpg over two or three tanks: miles driven divided by gallons filled.
Does a higher gas price change the gallons?
No: the price moves only the money. At $4.20 a gallon the same commute still burns 1.2 gallons a day, but the day costs $5.04 instead of $4.32.
What does the yearly figure leave out?
Everything but fuel: tolls, parking, servicing, tyres, insurance, and depreciation are all real commute costs that this calculator does not count. Treat $1036.80 as the fuel year, and add the rest separately.
How is this different from the driving-time calculator?
That page counts minutes for the same drive; this page counts dollars for the same drive. Use the time page for the schedule, this page for the budget.