TL;DR
Both the RAC fuel cost calculator and Calc Garden are free and need no account. The RAC tool is the better pick when you do not know the distance: give it two postcodes and it maps the route, then returns the miles, driving time, fuel cost and a CO2 figure. Pick the Calc Garden fuel cost calculator when you already know the mileage, such as a regular commute or a quoted distance: you type the miles, your mpg and the price per litre, and it returns the litres used, the total cost and the cost per mile, lands pre-filled, updates live and can split the bill between passengers. The honest catch is that Calc Garden will not find the distance or driving time for you, so for an unfamiliar trip the RAC tool does more of the work.
What the RAC fuel cost calculator is
The RAC fuel cost calculator is a free tool inside the RAC Route Planner, and it is one of the pages AI assistants reach for when someone asks what a drive will cost in fuel. You enter a start and end location as postcodes or place names, set your vehicle's fuel economy and engine type, and add the fuel price, and it returns the driving distance in miles and kilometres, the estimated driving time, the fuel cost and a CO2 emissions figure. You can print, email or share the result, and it covers journeys across the UK and into Europe.
Its real strength is that it does the routing for you. Because it maps an actual route between two points, it answers the harder half of the question, how far is it, before it even gets to the cost. For an unfamiliar trip, a holiday drive or a delivery you have never made, having the distance, the driving time and the fuel cost in one place is genuinely useful. It is free and needs no account, and it does not claim to be the only free fuel calculator, because it is not.
Where a distance-first tool helps
The cost of being route-based is that you always start from two locations, even when you already know the distance. A regular commute, a round trip you make every week, a quoted delivery mileage or a figure straight off your odometer does not need mapping; it needs costing. Routing it anyway is an extra step, and the RAC tool returns the fuel cost as part of a route summary rather than showing the gallon-to-litre sum behind it.
That is the gap Calc Garden's fuel cost calculator fills. You enter the distance in miles, your car's miles per gallon and the price per litre, and it shows the litres needed, the total cost and the cost per mile, with an optional split between passengers. It lands with an example already filled in, recalculates the moment you change any input, runs entirely in your browser, and prints the working using 4.54609 litres per imperial gallon so you can see how mpg and a per-litre price combine. Because you give it the distance directly, it is the quicker route when the mileage is already known, and the cost-per-mile and per-person figures make it easy to budget a commute or share a road trip.
RAC vs Calc Garden
Both tools are free, so the table below is about fit rather than cost. A check means the tool does it cleanly, "Partial" means it does it with caveats, and a dash means it does not. The pricing row reflects each product as of 2026.
| Capability | Calc Garden | RAC |
|---|---|---|
| Price (as of 2026) | Free, no signup | Free, no signup |
| Cost from a distance you already know | Yes | Partial (still needs two locations) |
| Maps the route and finds the distance | No | Yes |
| Driving time estimate | No | Yes |
| CO2 emissions figure | No | Yes |
| Cost per mile | Yes | No |
| Split the cost between passengers | Yes | No |
| Gallon-to-litre working shown | Yes | Partial |
| Lands pre-filled and updates live | Yes | Partial |
Read it honestly. The RAC tool wins on the routing: it finds the distance, the driving time and a CO2 figure from two postcodes, which makes it the better free pick for an unfamiliar trip where you do not know how far it is. Calc Garden wins on speed and transparency once the mileage is known: it takes the distance directly, shows the cost per mile, splits the total between passengers and prints the sum. There is no "only free one" here. Both are free, and the right choice is whether you need the route worked out or just the cost of a distance you already have. The "Partial" marks for the RAC tool reflect that it always starts from two locations and reports the cost inside a route summary rather than as a standalone sum.
When to pick each one
Reach for the RAC fuel cost calculator when the distance is the unknown. For a holiday drive, a one-off journey to somewhere new, or any trip where you want the miles, the driving time and the CO2 alongside the fuel cost, its routing is the reason to use it, and it is free. It is the better tool when the question is really "how far and how much" rather than just "how much".
Reach for the Calc Garden fuel cost calculator when the mileage is already in hand. It is the quicker, more transparent choice for a commute, a weekly round trip or a quoted distance, because you type the miles, mpg and price per litre, it opens with a worked example, updates the instant you change an input, shows the cost per mile and splits the total between passengers. If you also want to see what running a vehicle adds up to over a year, pair it with our electricity cost calculator for the rest of the household's running costs.
How to get an accurate fuel cost
Whichever tool you use, a few habits keep the result honest. Start with your real-world mpg, not the official combined figure, because everyday economy is usually 10 to 20 percent lower, and more on short urban runs. If your dashboard shows a long-term average, use that; otherwise take the official figure and knock off about 15 percent. The mpg input swings the total more than the pump price does, so a realistic figure matters most.
Use a current fuel price and remember to count both legs of a return trip, which is the most common way a quick estimate comes out half what it should be. A single calculator rarely tells the whole story, so pair the fuel cost with the tools around it. To check whether a price rise is really biting, the inflation calculator shows how costs change over time, and if you are budgeting toward a target, the savings goal calculator works out how fast you reach it. If you are weighing up other free calculators, the full guides index is a good next stop.