Ethanol-related Calculators

For the latest E85 prices in your area, visit

Gas vs E85: cost per mile, cost per year, etc

This calculator calculates the true costs of E85 and gas and will help you determine when the E85 pump is cost-effective.
E85 Price
Gas Price
Miles driven per year:
E85 cost per mile:
E85 miles per dollar:
Cost per year, fueled with E85:
Gas cost per mile:
Gas miles per dollar:
Cost per year, fueled with gas:
(To navigate the form via your keyboard, use "TAB" and "SHIFT TAB" keys.)

Blending ethanol and gas

For most vehicles, E10 (10% ethanol) yields worse mileage than gasoline without ethanol. What many people don't know is that E10 is probably the worst blend and for many vehicles, 20-30% ethanol will give you similar mileage to gasoline with no ethanol.1
Enter your gas tank size, previous ethanol %, and how much gas you added and this calculator will tell you the ethanol % in your tank. If you want to just calculate the results of mixing blends, check the "ignore vehicle" checkbox.
Note: the field after E0 allows for adding a custom value, like E100 or winter blend E80 or whatever you like that I missed.

Prior to filling

tank (gals) existing %
(If you're not filling your tank, uncheck this box.)


0.0% ethanol (or E0)

Gallons** added

gals E85 *
gals E70 *
gals E50
gals E40
gals E30
gals E25
gals E20
gals E15
gals E10
gals E0
gals E

(To navigate the form via your keyboard, use "TAB" and "SHIFT TAB" keys.)

* Note: in colder areas of the country, the actual percent of E85 gets downgraded to 70% during winter months.2

** You can substitute liters for gallons, if desired, without changing anything.

Octane result from blending 2 fuels

Trying to replace premium gas in a non-flexfuel vehicle? This tool's for you.
You should be able to find your octane numbers posted on the gas pump.3
Fuel #1
E85 (Gals)
E85 Octane *
% ethanol
Set octane to defaults 
Fuel #2
Gas (Gals)
Gas Octane *
% ethanol

* E85 typically has an octane of 105. E10 may vary from 87 to 93. Premium gas is typically 91. Racing fuel is often 100 or higher.