Distance + fuel → MPG (US/UK), L/100km, km/L, all at once + cost per mile/km — browser-only
- Runs locally
- Category Calculator
- Best for Getting a realistic range before a purchase, plan, workout, or schedule decision.
What this tool does
Free MPG calculator and fuel economy calculator. Enter how far you drove and how much fuel you burned, then read your real-world efficiency in every unit at once: miles per gallon (US), miles per gallon (UK/imperial), litres per 100 km, and kilometres per litre. Pick your input units — miles + US gallons, miles + UK gallons, or kilometres + litres — and the tool converts between all four readouts using exact factors (1 US gal = 3.785411784 L, 1 UK gal = 4.54609 L, 1 mile = 1.609344 km). Add a fuel price and it works out cost per mile, cost per kilometre, the spend to drive 100 mi or 100 km, and how far one full tank takes you. This is the tank-to-tank method drivers use to measure true consumption rather than trusting the dashboard average. Everything runs in your browser with a one-click copy and a shareable link. 100% client-side, nothing uploaded.
Tool details
- Input
- Numbers
- The page exposes text boxes, numeric controls, file pickers, or structured inputs depending on the tool.
- Output
- Live result + Copy
- The result area focuses on usable output, with copy, download, or preview actions when supported.
- Privacy
- Browser-side processing
- The main tool logic does not call an external API, so inputs normally stay in the current tab.
- Save / share
- Shareable URL state
- Key settings are encoded in the URL so another person can reopen the same setup.
- Performance budget
- Initial JS <= 9 KB
- No WASM budget is declared, keeping the tool quick to open on mobile.
- Best fit
- Calculator · Operations
- Category and role tags drive related tools, internal links, and quick fit checks.
How to use
-
1. Input
Paste or drop your content into the tool panel.
-
2. Process
Click the button. All processing is local in your browser.
-
3. Copy / Download
Copy the result or download to disk in one click.
How MPG Calculator fits into your work
Use it for fast estimates, comparisons, and planning numbers before you make the final call.
Calculation jobs
- Getting a realistic range before a purchase, plan, workout, or schedule decision.
- Comparing scenarios by changing one input at a time.
- Turning rough assumptions into a number you can discuss.
Calculation checks
- Double-check units, dates, rates, and rounding assumptions.
- Treat health, finance, tax, and legal outputs as planning aids, not professional advice.
- Save the inputs that produced an important result so you can reproduce it later.
Good next steps
These links move the current task into a more complete workflow.
- 1 Unit Converter Convert between length, weight, temperature, area, volume, speed, time — instant, browser-only Open
- 2 Currency Converter Currency converter — 50+ currencies with offline reference rates, convert without internet, source data updated each release. Open
- 3 Fuel Cost Calculator Trip fuel cost from distance + economy + price — round trip, per-person split, L/100km ⇄ MPG — browser-only. Open
Real-world use cases
Measure your car's real-world fuel economy
The dashboard average drifts and resets at the worst times. Do it the honest way: fill the tank, drive a normal week, fill again, and feed the trip miles and gallons in here. You get a true MPG you can trust, plus the L/100km figure for comparing against the spec sheet — which is almost always quoted in litres per 100 km outside the US.
Convert a US car's MPG for a UK or European buyer
A listing says 34 MPG and you are shopping from the UK. Is that US or imperial gallons? Punch the trip numbers in once and read 34 MPG (US) alongside its UK MPG and L/100km equivalents, so you can line it up against a locally-rated car without doing gallon math in your head at the dealership.
Budget a road trip's fuel cost before you leave
You know the route is 900 km and your car does about 6.5 L/100km. Add today's pump price and the tool gives cost per kilometre and the spend for the whole leg, plus how many full tanks the trip needs — so you can plan fuel stops and the budget instead of guessing at the first station.
Compare two cars or fuel grades on running cost
Deciding between a thirstier petrol and a frugal diesel, or testing whether premium fuel actually pays back? Enter each car's measured consumption and the matching fuel price, then read cost per mile side by side. The per-mile number cuts through gallon-vs-litre and US-vs-UK noise to the one figure that hits your wallet.
Common pitfalls
Mixing up US and UK gallons. They differ by about 20%, so a figure quoted in the wrong gallon throws MPG off by a fifth. Always pick the gallon that matches the pump you filled at before reading the number.
Measuring over a single partial tank. One short trip or a half fill-up gives a noisy result skewed by warm-up, terrain and pump cut-off. Use the full-tank method across two or three refills for a number that actually reflects how the car drives.
Confusing L/100km with km/L. L/100km goes DOWN as the car gets more efficient; km/L goes UP. Reading one as the other inverts your conclusion — a 5 L/100km car is great, but 5 km/L is terrible. Check the label before you compare.
Privacy
Every number — the MPG and L/100km conversions, the gallon-litre math and the fuel cost — is plain JavaScript running in your browser tab. Your mileage, fuel and price never leave the page and nothing is logged. The one caveat: the shareable link encodes your inputs and currency in the query string, so a "share link" pasted into chat records those figures in the recipient server's access log. For anything sensitive, use the copy button and paste the text instead of sharing the URL.
FAQ
Tool combos
Folks in your role tend to reach for these alongside this tool.
- AI Eval Planner Generate eval cases, pass criteria, and edge cases from an AI feature, risks, and user path.
- Annulus Area Calculator Area between two concentric circles — A = π(R² − r²), ring width, inner and outer circumference, solve backwards from area — browser-only
- Apache Cheatsheet Apache HTTP Server cheatsheet for httpd.conf, VirtualHost, .htaccess, mod_rewrite, SSL, proxying, auth, headers, and logs.
- awk + sed Cheatsheet awk + sed cheat sheet — 80+ one-liners for text processing, with real examples and common pitfalls.