Work out exactly how many gallons of E85 and pump gas to put in to hit your target ethanol blend — for a full fill, a top-up on what's already in the tank, or to check a mix you've already pumped.
Ethanol content varies — especially pump E85. Use what's on the pump or your test-kit reading.
Presets show the years they cover. Tap × on any preset — built-in or your own — to delete it, or add your own vehicle.
All built-in presets deleted — you can restore them under Menu → My vehicles.
Saved on this device — your added vehicles will be here next visit. Manage them under .
Pick the situation — the answer updates as you type.
The calculator fills the rest of the tank to full and works out the split for the space that's left.
Native store apps for Windows and Android, so you can download, rate, and review it where you normally get apps. On iPhone and iPad, use the web app for now — same calculator, no download needed — until the iOS version is published officially.
A standalone Windows app that launches in its own window — no browser tabs to hunt for. The Microsoft Store listing is the point: anyone who uses it can leave a rating and a review there.
Until the store build lands, this web version also installs from Edge or Chrome: ⋯ / ⋰ menu → Apps → Install this site as an app (wording varies by browser).
A native Android app for Google Play, built from this same calculator — same targets, same fill / top-up / check modes, same math. Play Store ratings and reviews are built into that route.
In the meantime, open this page in Chrome and use ⋮ menu → Install app / Add to Home screen to pin it like an app.
iOS joins via the web app until the App Store version can be published officially. It runs full-screen from your Home Screen and needs no account:
When the iOS app is published, it will move to the App Store too — with ratings and reviews there, just like the other stores.
Pump E85 is the big variable. Its actual ethanol content swings with season and station (51–83% by US spec), which is why this calculator lets you change it. A cheap ethanol test kit — or a flex-fuel sensor / ethanol gauge if your tune supports one — takes the guesswork out.
The math is a straight volume blend: total ethanol in ÷ total fuel in. It assumes the two fuels mix evenly and ignores the tiny volume change when ethanol and gasoline combine — close enough for any pump fill.
Don't run a blend your tune isn't written for. Higher ethanol needs more fuel volume; on a stock or 93-octane tune, a strong blend can run the car lean. Only run E30 on an E30 (or flex-fuel) tune.
Your saved vehicles and stations, plus the rest of the app.
Vehicles and stations are saved in this browser on this device, so they're here the next time you open the app on it.
Choose how the app looks. Your choices apply straight away and are saved on this device between visits.
Light or dark — or System, which follows your device setting and changes with it.
Currently showing: —
Preset combinations for the two fuel colours — the first colour is E85, the second is pump gas. Every scheme is designed for both light and dark themes.
Try a scheme with both themes — each one adjusts its shades so text stays easy to read in light and dark.
Tap a vehicle to use its tank size in the calculator. You can delete any vehicle here — built-in presets and vehicles you've added. Deletions and added vehicles are saved on this device between visits.
Save the stations you visit. For each fuel a station offers, record its ethanol content as Tested — a true, measured value — or Rated — what the pump / station says, assumed. Apply any fuel straight to the calculator, or tap Navigate on a saved station to get directions in your maps app.
Looking for a station that sells E85? Open the in-app finder — it searches the US Department of Energy's E85 station database and shows results on a map, with distances. Save any result and it lands in your stations below.
Tested vs. Rated: “Tested” means you measured it yourself (test kit or sensor) — treat it as the true content. “Rated” is the station's posted value or the usual assumption for that fuel (for example E85 rated 85%, premium rated 10%) until you've tested it.
Stations that sell E85, from the US Department of Energy's Alternative Fuels Data Center (AFDC) — the purpose-built database for alternative-fuel stations, instead of a general map search. Results are public stations only, nearest first.
Your location is used only to run the search — it is never saved or stored. Station data: US DOE / National Laboratory of the Rockies (NLR) AFDC. Listings can lag the real world when a station adds or drops E85, so if a trip depends on it, it's worth a quick call ahead.
Map tiles couldn't load — the station list below still works.
Every change and update to this app, newest first.