Fuel Range Calculator

Related Calculators

Table of contents

• How to use
• Common mistakes
• Definitions
• Methodology
• Limitations & assumptions
• Sources

Tank size: The usable amount of fuel your vehicle can hold, measured in gallons.

Fuel economy: How many miles the vehicle travels per gallon of fuel. Official MPG is a distance-per-fuel measure [1].

Current fuel level: Your estimated fuel gauge reading as a percent of a full tank.

Safety buffer: Fuel you choose not to plan on using, so the safer stop distance does not count the last part of the tank.

MPG reduction: A percent decrease applied to your MPG for conditions that can lower real range, such as hills, high speed, heavy cargo, towing, or cold weather.

MPG used for this estimate: Your entered MPG after any MPG reduction for tough conditions.

Plan fuel stop within: The miles available before you reach the chosen safety buffer. A value of 0 means the buffer is already reached or passed.

Miles per $1: The adjusted MPG divided by gas price, showing how many miles one dollar of fuel buys.

Mistake: Entering a dashboard range estimate into Fuel economy (miles per gallon).
Fix: Enter MPG, such as 30, not miles left, such as 210.

Mistake: Using a decimal for Current fuel level (percent), such as 0.5 for half a tank.
Fix: Enter 50 for half a tank, 25 for one quarter, or 75 for three quarters.

Mistake: Setting Fuel to keep as a safety buffer (gallons) larger than Tank size (gallons).
Fix: Use a buffer from 0 up to your tank size, such as 1.5 gallons on a 14-gallon tank.

Mistake: Leaving MPG reduction for tough conditions (percent) high after using it for a hard trip.
Fix: Set it back to 0 for normal driving, or enter a smaller percent for mild hills, cold weather, or heavy cargo.

Mistake: Typing a total fill-up price into Gas price ($ per gallon).
Fix: Enter the pump price per gallon, such as 3.50, so Estimated cost to fill up and Miles per $1 make sense.

• The calculator treats Current fuel level (percent) as a straight-line estimate. Real fuel gauges are often less exact near full or empty.
• Fuel economy can change during the trip because of speed, traffic, hills, wind, tire pressure, cargo weight, towing, and temperature.
• Tank size should be the usable fuel capacity. If you use a larger published or rounded capacity, range can be overstated.
• The safety buffer is a planning choice, not a guarantee. Keep a larger buffer in remote areas, bad weather, or heavy traffic.
• Gas price only affects Estimated cost to fill up and Miles per $1. It does not change Estimated miles left.
• The Plan fuel stop within result is floored at 0 because a distance before reaching the buffer cannot be negative.

How the calculator works

The calculator first adjusts the entered Fuel economy (miles per gallon) if you entered an MPG reduction for tough conditions (percent). It then estimates gallons in the tank from Tank size (gallons) and Current fuel level (percent). MPG is treated as miles traveled per gallon of fuel [1].

effective_mpg = mpg * (1 - mpg_reduction_percent / 100)

fuel_remaining_gallons = tank_gallons * (fuel_level_percent / 100)

remaining_range_miles = fuel_remaining_gallons * effective_mpg

The safer trip-planning result subtracts the Fuel to keep as a safety buffer (gallons) before converting fuel to miles. If the buffer is already reached, the result is 0.

plan_stop_within_miles = max(0, (fuel_remaining_gallons - reserve_gallons) * effective_mpg)

Full-tank range and fill-up estimates use the same adjusted MPG and current fuel amount.

full_tank_range_miles = tank_gallons * effective_mpg

gallons_to_fill = tank_gallons - fuel_remaining_gallons

If Gas price ($ per gallon) is entered, the calculator also estimates cost and miles bought per dollar.

cost_to_fill = gallons_to_fill * gas_price

miles_per_dollar = effective_mpg / gas_price

Mini-example

For a 14-gallon tank, 30 MPG, 50 percent fuel level, a 1.5-gallon safety buffer, and 0 percent MPG reduction, the fuel left is 7 gallons. Estimated miles left is 7 * 30 = 210 miles. The safer stop distance is (7 - 1.5) * 30 = 165 miles.

Input checks

The calculator blocks impossible entries: Tank size (gallons) and Fuel economy (miles per gallon) must be greater than 0, Current fuel level (percent) must be from 0 to 100, the safety buffer must be from 0 up to the tank size, MPG reduction must be from 0 to 80, and Gas price ($ per gallon) must be blank or greater than 0.