The calculators in this section answer three separate questions that get lumped together under "travel costs": what it costs to run your own vehicle for a given trip, what it costs to pay someone else to move you instead, and how long the trip actually takes once it is not just distance divided by a speed limit. The three use genuinely different arithmetic, and mixing them up is the most common way a travel budget or a journey plan ends up wrong.
Calculators in this section
Fuel cost is consumption times distance times price — if the units match
Fuel cost for a trip comes down to three numbers multiplied together: how much fuel the vehicle uses per unit of distance, how far the trip is, and the price per unit of fuel. The catch is that "how much fuel per distance" is measured at least three incompatible ways depending on where you learned to drive — miles per US gallon, miles per UK imperial gallon (about 20% larger than a US gallon), and litres per 100 kilometres, which runs the opposite direction from the other two since a lower number means better efficiency rather than worse. The fuel consumption calculator handles the conversion between them; the UK-specific fuel cost calculator works directly in litres and pence per litre, which is how fuel is actually priced and pumped in the UK, rather than forcing a gallons-and-dollars figure into a market that does not use either.
Journey time is not distance divided by the speed limit
A route's posted speed limit is the maximum permitted speed for the fastest stretch of it, not the average speed for the whole trip — traffic lights, roundabouts, congestion and the difference between a motorway and a city street all pull the real average down, often substantially, on exactly the same route. That is why journey time and journey distance are two separate calculators here rather than one combined figure: distance is fixed by the route, but time depends on an average speed assumption that has to be supplied separately and adjusted for the kind of road actually being driven.
Ride-hailing fares and transit fares price the trip differently
An Uber-style fare is built from a base charge plus a rate per mile and per minute, then multiplied by a surge factor when demand in the area is running ahead of available drivers — which is why the same route can produce noticeably different quotes an hour apart with nothing about the distance having changed. London's Oyster card works on the opposite principle: fares are set by which zones a journey crosses rather than by distance travelled within them, and Transport for London's fare capping automatically charges no more than the cheapest equivalent Travelcard for a day or week of travel once enough taps have accumulated, which the Oyster fare calculator accounts for rather than just multiplying a per-journey price by the number of trips.
Why it is worth running more than one of these together
A real trip usually needs two or three of these figures at once rather than just one. Comparing driving against a ride-hailing service for the same journey means running a fuel cost calculation and a fare estimate side by side, not picking one method and assuming it represents the alternative fairly — a car that is already owned and insured has a much lower marginal cost per trip than the fuel cost alone suggests, since the fuel figure leaves out depreciation, insurance and maintenance that keep accruing whether or not the car is driven. Journey time matters just as much as either cost figure whenever a trip has to arrive by a specific point, which is the reason the distance and time calculators are kept separate rather than folded into a single "how long and how much" tool: distance is fixed by the route, but the time and cost figures both depend on assumptions worth checking independently before they are added together.