Why does EV range drop faster at higher speeds than MPG in petrol cars?

Aerodynamic drag rises with the square of speed for both, but EVs lack a multi-gear transmission to keep the motor in its efficiency sweet-spot; electric motors also draw more current at higher power, increasing resistive losses. Petrol engines waste much of their fuel as heat even at low load, so the marginal penalty of higher speed is proportionally smaller.

Where do I find my vehicle's range loss per 10 mph?

Some manufacturers publish range tables at 55, 65, 70 and 80 mph. Divide the difference in range by the speed step and convert to a percentage of the 70 mph figure. Alternatively, track multiple motorway trips at constant speeds using the trip computer and calculate the loss yourself.

Can I use this calculator for speeds below 70 mph?

Yes. Enter a target speed lower than 70 and the tool will show increased range. The linear model is less accurate below 40 mph because city stop-start cycles and accessory loads become significant, neither of which the formula includes.

Does cold weather affect the result?

The calculator does not adjust for temperature. In practice, battery chemistry and cabin heating can reduce range by 20–40% below freezing, on top of any speed penalty. Treat the output as a temperate-weather baseline and apply an additional cold-weather factor if needed.

Why is there a clamp on the cumulative loss percentage?

At very high speeds (e.g. 150 mph) a fixed percentage per 10 mph would predict negative or near-zero range, which is physically implausible. The −50% to +90% clamp keeps results within a plausible band and prevents the linear approximation from breaking down at the extremes.

EV vs ICE

EV Range Cost by Speed

Calculate how highway speed changes your EV's real-world range using a linear loss model.

Last updated: 25 June 2026

What this tool does

This calculator applies a linear speed-penalty model to estimate electric-vehicle range at speeds above or below 70 mph. You enter your vehicle's rated range at 70 mph, the percentage range loss per 10 mph increment (typically 10–15% for modern EVs), and your target cruising speed; the tool returns projected range in miles. The linear model approximates real-world aerodynamic and rolling-resistance effects but does not account for temperature, terrain, or accessory loads.

Inputs

Result

—

Continue with your figures

These calculators share inputs with this one. Change a value above and your figures travel with the link, in the part of the URL your browser never sends to a server.

Speed vs Fuel Consumption

Fuel & Efficiency

Calculate how highway speed affects your fuel economy using a percentage-drop model.

Formula

R = R_{70} \times (1 - \frac{L \times ( \frac{v - 70}{10} )}{100})

R

Projected range at target speed

R_{70}

Rated range at 70 mph

L

Range loss per 10 mph increment

v

Target speed in mph

How EV Range Cost by Speed works

Electric-vehicle range drops sharply as speed rises, chiefly because aerodynamic drag grows with the square of velocity. This calculator models that effect using a constant percentage loss for each 10 mph above (or gain below) a 70 mph baseline. You supply three numbers: your EV's rated range at 70 mph, the observed or manufacturer-quoted range penalty per 10 mph step, and the highway speed you plan to sustain. The tool multiplies the number of 10 mph steps by your loss percentage, then scales the baseline range accordingly.

The formula

Range_speed = Range₇₀ × (1 − steps × loss% / 100)
where steps = (target_speed − 70) / 10. If you travel slower than 70 mph, steps becomes negative and range increases. The code clamps the cumulative loss percentage between −50% and +90% to prevent nonsensical outputs at extreme speeds.

Where this method is most accurate

The linear loss assumption fits highway cruising between roughly 55 and 85 mph, where aerodynamic drag dominates and HVAC load is steady. Below 40 mph city driving introduces stop-start losses not captured here. Above 90 mph the quadratic nature of drag means each additional 10 mph costs more than the last, so a fixed percentage underestimates the penalty. Temperature below 40°F or above 95°F, steep grades, and high-speed headwinds all reduce range beyond what the formula predicts.

What this tool does not do

It does not model battery-temperature effects, regenerative braking in hilly terrain, cabin heating or cooling draw, tyre pressure, or payload weight. It assumes constant speed on level ground in moderate weather. The calculator also does not verify whether your entered loss-per-10-mph figure matches your specific vehicle; published manufacturer range tables or real-world logs remain the authoritative source for that parameter.

Disclaimer

This tool is for educational estimation only. It does not constitute vehicle-range certification, trip-planning advice, or a guarantee of drivable distance. Real-world range depends on driving style, weather, battery state-of-health, and road conditions. Always plan charging stops with a safety margin and consult your vehicle's onboard range computer for live estimates.

Questions

Why does EV range drop faster at higher speeds than MPG in petrol cars?: Aerodynamic drag rises with the square of speed for both, but EVs lack a multi-gear transmission to keep the motor in its efficiency sweet-spot; electric motors also draw more current at higher power, increasing resistive losses. Petrol engines waste much of their fuel as heat even at low load, so the marginal penalty of higher speed is proportionally smaller.
Where do I find my vehicle's range loss per 10 mph?: Some manufacturers publish range tables at 55, 65, 70 and 80 mph. Divide the difference in range by the speed step and convert to a percentage of the 70 mph figure. Alternatively, track multiple motorway trips at constant speeds using the trip computer and calculate the loss yourself.
Can I use this calculator for speeds below 70 mph?: Yes. Enter a target speed lower than 70 and the tool will show increased range. The linear model is less accurate below 40 mph because city stop-start cycles and accessory loads become significant, neither of which the formula includes.
Does cold weather affect the result?: The calculator does not adjust for temperature. In practice, battery chemistry and cabin heating can reduce range by 20–40% below freezing, on top of any speed penalty. Treat the output as a temperate-weather baseline and apply an additional cold-weather factor if needed.
Why is there a clamp on the cumulative loss percentage?: At very high speeds (e.g. 150 mph) a fixed percentage per 10 mph would predict negative or near-zero range, which is physically implausible. The −50% to +90% clamp keeps results within a plausible band and prevents the linear approximation from breaking down at the extremes.

Spotted something off?

Calculations or display — let us know.

Sources & Methodology

The tool calculates steps = (target_speed − 70) / 10, then applies cumulative_loss = loss_per_10mph × steps, clamped between −50% and +90%. Final range = rated_range_70 × (1 − cumulative_loss / 100). This linear step model approximates the non-linear speed–energy relationship observed in EPA and WLTP range testing over typical highway speeds.

Related tools

EV vs Petrol Total Cost (5yr)

Compare total cost of ownership—purchase price, fuel, and depreciation—for EV vs petrol over 1–20 years.

Charging Time Calculator (kW input)

Calculate EV charging time from any start % to any target %, given battery size and charger power.

EV vs Petrol Fuel Cost

Compare annual electric vs petrol fuel costs using your efficiency figures and local energy prices.

EV Charging Cost Per Mile

Calculate the electricity cost to drive each mile in your EV based on efficiency and your kWh rate.

Battery Replacement Cost Projection

Project the future cost of an EV battery replacement using annual price-decline rates.

Public vs Home Charging Cost

Calculate your annual EV charging cost when you split between public chargers and home electricity.

People also use

Monthly Car Payment Calculator

Financing & Purchase

Calculate your monthly car loan payment from loan amount, APR, and term in months.

Fuel Cost for a Journey

Fuel & Efficiency

Calculate the total fuel cost for a journey from distance, MPG, and fuel price per litre.

Loan vs Lease Comparison

Cost of Ownership

Compare total cost of buying on finance versus leasing over different terms and buyout scenarios.

Braking Distance Calculator

Performance & Engineering

Calculate total stopping distance from speed, road friction and driver reaction time.

Long Road Trip Total Cost

Practical & Utility

Calculate total fuel, lodging, food, and toll expenses for a multi-day road trip.

Depreciation % Retained Calculator

Resale & Depreciation

Calculate what percentage of its original value a car has retained after depreciation.