Highway driving representing how to estimate driving range on a tank using MPG and tank size

How to Calculate Driving Range on a Tank (and Add a Safety Buffer)

February 23, 2026 10 min read

Quick Summary Driving range on a tank is a simple formula: tank size × MPG. The hard part is choosing a realistic MPG (because speed, traffic, weather, and maintenance change it) and deciding on a safety buffer so you don't run the tank extremely low.

Range estimate (miles) = usable gallons × MPG.
Use your real-world MPG if you have it; otherwise start with EPA label values and refine.
For road trips, plan refuel stops with a buffer instead of assuming you can use every last mile of rated range.

What We Know (Sourced)

EPA label values are produced using standardized testing intended to support comparisons, and the EPA notes that real-world results vary with conditions like speed, temperature, traffic, load, and accessory use.

DOE consumer guidance on fuel economy provides context for why real-world MPG changes and why efficiency improvements (maintenance, driving behavior) can shift your fuel cost and range outcomes.

Range planning is math + realism: The math is easy. The realism comes from choosing MPG and building in a buffer for conditions you can't perfectly predict.

The Range Formula

Estimated range (miles) = usable gallons × MPG

Use tank capacity from your owner's manual and a realistic MPG value

If you want to calculate it instantly with unit conversions and remaining fuel level, use our tool: Fuel Tank Range Calculator.

How to Pick a Realistic MPG

Best options, in order:

Your own measured MPG (tank-to-tank, averaged over multiple fill-ups).
EPA label values (City/Highway/Combined) as a baseline.

Related guides:

Adding a Safety Buffer

Even with good inputs, your range varies by conditions. For trip planning, many drivers choose to refuel before the tank is extremely low. The exact buffer is a personal risk-management choice and should be guided by your vehicle manual and route constraints.

For road trips, the next step is converting "range on tank" into "where do I stop." Related: planning fuel stops.

Planning a long trip?

Estimate fuel needed and cost, then layer in range-based stop planning.

Try the Fuel Cost Calculator

What's Next

Measure your MPG for a few weeks so your range estimate matches your real driving.
Use a buffer on unfamiliar routes, in winter, or where fuel stations are sparse.
If range is unexpectedly low: check maintenance basics like tire pressure. Related: maintenance checklist.

Frequently Asked Questions

Why does my real range differ from my estimate?

Because your MPG changes with speed, traffic, weather, load, and accessory use. EPA notes label values are standardized comparisons and real-world results vary with conditions.

Should I use City MPG or Highway MPG for range?

Use the MPG that matches how you'll actually drive. For a mostly freeway trip, Highway MPG is a better baseline. For mixed driving, Combined MPG is a reasonable start.

Can I do the same range math for an EV?

Yes, but the inputs change. Instead of gallons, you use battery kWh and kWh per mile, and range can be more sensitive to temperature. Related: EV range in cold weather.