Gas Cost Calculator
The drive, the car and the pump
Your result will appear here
Fill in the fields on the left and this updates as you type.
Know what this estimate is based on
- Jurisdiction
- General mathematical model
- Scope and limitations
- Planning indicator only. It does not assess every part of a household's finances or replace individualized professional advice.
- Source links checked
- Jul 30, 2026
Built and regression-tested by Smart Tools Lab. It has not been individually reviewed by a licensed financial, tax, or legal professional.
How to use
- 01
Enter the distance in miles. It takes one leg or the whole drive, whichever number you happen to have — the page reports the doubled there-and-back figure either way, so it does not matter which you typed.
- 02
Enter your vehicle's MPG. Use your own average from a full tank rather than the window sticker, because the per-mile cost is the pump price divided by this number and a 20% error here is a 20% error in the answer.
- 03
Enter today's price a gallon. The table below then reprices the same drive across a dollar-wide band, from 50 cents under to 50 cents over, which settles the cheap-station argument before it starts.
- 04
Enter how many people are splitting the gas, including yourself, and any tolls and parking for this trip. Gas is the one part of a drive that genuinely divides by the number of people in the car.
- 05
Open Advanced options to blend a highway MPG against the city figure with the highway share of the drive, and to set the IRS standard mileage rate — $0.70 for 2025, reset each December — which the page uses as the yardstick for everything a drive costs that is not fuel.
Formula
Gallons = miles ÷ MPG. Where you give both a city and a highway figure, the drive is split first: highway miles = miles × the highway share, city miles are the rest, and gallons = city miles ÷ city MPG + highway miles ÷ highway MPG. The blended MPG is then miles ÷ gallons — weighted by miles, not by the two MPG figures. Cost = gallons × price a gallon. Cost per mile = cost ÷ miles, which is the same thing as price ÷ MPG. There and back = 2 × cost. Each passenger owes cost ÷ the number of people in the car. Out of pocket = cost + tolls and parking. The same miles at the IRS standard rate = miles × the rate. Dividing that rate by your cost per mile gives the multiple — how many times the pump cost the full cost of running the car comes to. What 25 cents at the pump does = gallons × $0.25. Note that it scales with GALLONS, not with miles, which is why a thirsty car cares about pump prices and an efficient one does not.
Example
A 320-mile drive, 28 MPG, $3.15 a gallon, one person, no tolls. It uses 11.43 gallons and costs $36.00 — $0.113 a mile, $72.00 there and back on 640 miles and 22.86 gallons. The same 320 miles at the 2025 IRS standard rate of $0.70 come to $224.00, about 6.2 times the fuel, because that rate covers depreciation, insurance, maintenance and tyres as well as gas. A 25-cent move at the pump is worth $2.86 on this drive, and the table prices the whole band: $30.29 at $2.65 a gallon through $41.71 at $3.65. Five more MPG would take it to $30.55, a saving of $5.45. Change the inputs to four people, $18.00 of tolls, and a blend of 34 MPG on the highway across 80% of the distance: the drive now uses 9.82 gallons at a blended 32.6 MPG, costs $30.92, works out at $0.097 a mile, is $7.73 a head, and comes to $48.92 out of pocket with the tolls in.
Definitions
- MPG
- Miles per gallon. The single number the whole answer turns on — cost per mile is simply the pump price divided by it, so an optimistic MPG produces an optimistic drive.
- Blended MPG
- One economy figure for a mixed drive, weighted by miles rather than by the two MPG numbers. A mostly-highway trip sits close to the highway figure, not halfway between.
- Cost per mile
- The fuel cost of a mile: price a gallon ÷ MPG. It is the fuel-only figure, and it is several times smaller than what a mile of driving really costs.
- IRS standard mileage rate
- The per-mile figure a business driver may deduct — $0.70 for 2025, reset by the IRS each December. It is built to cover depreciation, insurance, maintenance, tyres and repairs as well as fuel, which is why it dwarfs the pump number.
- Pump-price swing
- What a 25-cent move at the pump does to this drive: gallons × $0.25. It scales with gallons rather than with miles, which is why it is usually smaller than the detour taken to chase it.
Good to know
MPG is the number the answer turns on, and the sticker's is optimistic
Cost per mile is the pump price divided by your MPG, which means an error in the MPG is an error of the same size in every figure on the page. It is worth getting right, and the window sticker is not the place to get it. The combined figure on a new car's label comes from a standardised EPA test cycle, and real driving differs from it in ways that all point the same direction: sustained speeds above about 70 mph, air conditioning in summer, a car loaded for a trip, a roof box, short cold trips where the engine never reaches temperature, winter-blend fuel, and under-inflated tyres. Ten to twenty per cent below the sticker is ordinary rather than alarming. Measuring your own takes exactly one tank and no equipment: fill up, zero the trip meter, drive normally, fill up again at the same pump style, and divide the miles shown by the gallons it took to refill. Do it once on a long highway tank and once across a week of local driving and you have both numbers the Advanced blend wants, which is the only way this page can tell a mostly-interstate drive from a mostly-town one. Cars that report an average MPG on the dash are usually optimistic by a few per cent, so a tank measured by hand beats the display when the two disagree.
Gas is the cheap part of a mile
The default drive on this page — 320 miles at 28 MPG and $3.15 a gallon — uses 11.43 gallons and costs $36.00, which is $0.113 a mile. The IRS lets a business driver deduct $0.70 a mile for 2025, roughly 6.2 times as much, and the difference is not margin or padding. The standard rate is constructed to cover the whole cost of operating a vehicle: depreciation, which is usually the largest single component and is invisible because nobody writes a cheque for it; insurance; maintenance and repairs; and tyres — alongside fuel, which is the smallest term in the set. So the same 320 miles that cost $36.00 at the pump cost something closer to $224.00 once the car itself is counted. Two practical consequences follow. If an employer or a client reimburses at the standard rate, the reimbursement is not a windfall on top of your gas; it is compensation for wear you cannot see happening. And if you are riding in somebody else's car for a long trip, splitting the gas four ways is generous to you rather than to them, because the depreciation and the wear happen once regardless of how many people are in the back. The IRS resets this rate every December, so the figure is a field on the page rather than a constant.
Chasing the pump price, and what it is actually worth
The saving from a cheaper station scales with GALLONS, not with miles, and that single fact settles most arguments about it. Twenty cents a gallon on a 12-gallon fill is $2.40, full stop — it does not matter how far you are driving afterwards. The detour to reach it costs your cost per mile times the extra distance, plus the time: five miles out of the way at $0.113 a mile spends $1.13 of that $2.40 before you have parked, and ten miles spends most of it. The corollary is that pump-price sensitivity is really a property of the vehicle. A 25-cent move changes this 320-mile drive by $2.86 because it burns 11.43 gallons; the same move on a trip burning 30 gallons is $7.50. The table on the page prices the whole band from $2.65 to $3.65 a gallon so the argument can be settled before it starts: end to end that dollar of pump price is worth $11.42 on this drive, against a $36.00 base. Worth knowing, not worth a fifteen-minute detour. Where pump price genuinely matters is the fill you were going to make anyway — the station you pass daily, the app that shows the corridor, the membership price at a club you are already visiting — because that saving costs nothing to collect.
Speed, the blend, and the levers that actually work
Aerodynamic drag rises with the square of speed, so the power needed to push a car through the air rises steeply once it dominates rolling resistance — which is why economy falls off sharply past roughly 55 to 65 mph and why 'highway miles' at 80 mph are not the sticker's highway miles. Speed is therefore the largest single lever available on a trip already underway, and the honest framing is a trade: driving 320 miles at 65 rather than 75 costs about forty minutes and saves real fuel. The blend field exists because that same effect makes one MPG number wrong for a mixed drive, and the important detail is that the blend is weighted by MILES rather than by the two MPG figures — a drive that is 80% interstate sits close to the highway number rather than in the middle. On this page's numbers, 320 miles at 80% highway with 28 MPG in town and 34 on the interstate blends to 32.6 MPG and $30.92 instead of $36.00. The remaining levers are unglamorous and real: tyres at the door-jamb pressure rather than the sidewall maximum, the roof box or bike rack removed when it is empty, and the weight that has been in the trunk since March. Five more MPG takes this drive from $36.00 to $30.55. None of that is an argument for a different car — that is a separate question, and a separate page.
Frequently asked questions
How much gas will this trip use?
Miles divided by MPG. A 320-mile drive at 28 MPG uses 11.43 gallons, and at $3.15 a gallon that is $36.00 one way, $72.00 there and back. The gallons figure is the one worth carrying, because it is the multiplier on every pump-price question: a 25-cent move at the pump changes this drive by 11.43 × $0.25 = $2.86, whatever the price happens to be.
What MPG figure should I use?
Your own, measured. The combined number on the window sticker assumes an EPA test cycle, and a loaded car on a hot day with the air conditioning running, at 78 mph, on winter-blend fuel, does worse — frequently by 10% to 20%. Measuring it takes one tank: fill up, zero the trip meter, drive normally, fill up again, and divide the miles by the gallons it took to refill. Do it on a long highway tank and a week of local driving and you have both numbers the Advanced blend wants.
What does a mile of driving actually cost?
In gas alone, the pump price divided by your MPG: $3.15 ÷ 28 is $0.113 a mile. That is the small number. The IRS lets a business driver deduct $0.70 a mile for 2025 — roughly 6.2 times as much — and the gap is not margin. The standard rate is built to cover depreciation, insurance, maintenance, tyres and repairs as well as fuel, so the same 320 miles that cost $36.00 at the pump cost something closer to $224.00 once the car itself is counted.
Is it worth driving out of my way for cheaper gas?
Almost never, and the arithmetic is quick. The saving is the price gap times the GALLONS you buy, not times the miles you drive: 20 cents a gallon on a 12-gallon fill is $2.40. The detour costs the price per mile times the extra miles, plus the time. Five miles out of the way at $0.113 a mile spends $1.13 of the $2.40 before you have parked. The whole dollar-wide band the table prices — $2.65 a gallon up to $3.65 — moves this drive by $11.42 from end to end, which puts the size of the argument in perspective.
How should passengers split the gas?
Divide the fuel cost by everybody in the car including the driver — $36.00 four ways is $9.00 each, or $18.00 each for the round trip. What is worth knowing is that gas is the ONLY part of a drive that divides. The depreciation and the wear happen once, whoever is sitting in the back, so a driver splitting fuel four ways is still carrying most of the real cost. For a long trip in somebody else's car, splitting at the IRS rate instead is the honest number: $224.00 four ways is $56.00 a head.
Does blending city and highway MPG make much difference?
It can move the total by 10% to 20%, because the two figures differ by that much on most cars. The important part is that the blend is weighted by MILES rather than by the two MPG numbers, so a mostly-highway drive sits close to the highway figure rather than in the middle: 320 miles at 80% highway, 28 MPG in town and 34 on the interstate, blends to 32.6 MPG and $30.92 rather than $36.00. Above roughly 55 to 65 mph aerodynamic drag rises with the square of speed, so 'highway' miles at 80 mph are not the sticker's highway miles.
What actually improves MPG on a single trip?
Speed, pressure and weight, in that order. Holding nearer 60 than 80 is the largest single lever, because drag rises with the square of speed and economy falls off sharply past about 55 to 65 mph. Tyres at the door-jamb pressure rather than the sidewall maximum. The roof box or bike rack that comes off when it is empty. The weight in the trunk that has been there since March. Five more MPG on this drive takes it from $36.00 to $30.55 — real, but smaller than the difference speed alone can make.
Does this work for an electric car?
No, and deliberately so. This page prices one drive in gallons of gasoline. Comparing a gas car against an electric one is a drivetrain question with a purchase-price difference to pay back, and it lives on the gas-versus-electric page. If the drive is the same one five days a week, the number that matters is the annual one with wear and parking in it, which is the commute cost page. Both modes would make this page slower at the only job it has.