EV Winter Range, Tread Depth and MPG Converter

EV range drops 40-53% in winter. 3 mm tread doubles wet braking. 30 US MPG is 36 UK MPG. Three automotive calculators with data, formulas and examples.

Krystian Szyszka · 8 August 2026 · 10 min read

A 60 kWh battery rated at 400 km on the WLTP cycle. PTC heater running, winter tires on, mixed city-highway route, -10C outside. Real range: 190 km. That is not a worst-case scenario. That is Tuesday morning in January.

The 53% loss breaks down like this: temperature chemistry accounts for 35 percentage points, the PTC heater adds another 67%, winter tires contribute 4% and mixed driving 5%. Stack them together and your consumption jumps from 15 to 31.6 kWh per 100 km. The 400 km promise on the sticker quietly becomes a 190 km reality on the road.

Three numbers every driver should know before winter arrives. How far the battery actually goes. How much rubber sits between the car and the road. And whether the MPG number on a review page uses a US gallon or a UK one - because the answer changes by 20%.

The battery does not freeze - it slows down

Lithium ions move through electrolyte like swimmers through water. Cold water is thicker. At -10C, the internal resistance of a lithium-ion cell rises enough to cut available energy by roughly 35% before you even turn on the heater.

Then the heater kicks in.

A PTC resistive heater draws 3.5-4.5 kW continuously. At a mixed-route average speed of 45 km/h, that heater consumes as much energy as the drivetrain. The calculator shows it clearly: the heating penalty alone is 67% - meaning the heater adds 10 kWh per 100 km on top of the base 15. A heat pump cuts this roughly in half, drawing 1.5-2 kW instead of 4.5.

FactorPenaltyLost range
Temperature -10C (battery chemistry)+35%-66 km
PTC cabin heater at 45 km/h avg.+67%-127 km
Winter tires (rolling resistance)+4%-8 km
Mixed route (vs WLTP cycle)+5%-9 km
Preconditioning (off)0%0 km
Total+111%-210 km

Preconditioning while plugged in recovers about 5% - not dramatic, but free. It warms the battery using wall power, which means better cell efficiency from the first kilometer and faster regen braking. The real trick is the heat pump. Switching from PTC to heat pump in the calculator drops the total penalty from 111% to about 60-70%. That is the difference between 190 km and 250 km on the same battery.

EV Winter Range Calculator showing 60 kWh battery at -10C dropping from 400 km WLTP to 190 km real winter range

The temperature table inside the calculator tells the full story. At +20C you get the full 400 km. At 0C it drops to 210. At -20C - 177 km. That is less than half the sticker number, and it is not a defect. It is physics.

How far does your EV go in winter?

Pre-filled calculations for specific temperatures - enter your battery and see the result instantly:

4.2 mm of tread looks fine - until it rains

A new summer tire has 8 mm of tread depth. At 4.2 mm, you have used 59% of the usable tread (measured against the 1.6 mm legal minimum). The tire passes every inspection. It looks fine on a dry road. And on wet asphalt at 80 km/h, it needs roughly 30-40% more distance to stop compared to a new tire.

The math is straightforward. Each millimeter of tread channels water away from the contact patch. Less depth means less drainage capacity. At some point - around 3 mm for summer tires, 4 mm for winter - the grooves can no longer evacuate water fast enough and the tire starts hydroplaning at speeds where a new tire still grips.

Tread depthStatusWet braking penaltyAction
8 mmNew0%None needed
6 mmGood+5-10%Monitor
4 mmAdequate+15-25%Replace winter tires
3 mmReplace soon+30-40%Replace all tires
2 mmCritical+50-60%Replace immediately
1.6 mmLegal limit+80-100%Illegal below this

The calculator caught something else in our test: the edge measured 3.5 mm while the center read 4.2 mm - a 0.7 mm difference. That pattern means underinflation or a wheel alignment problem. The tread wears faster on the edges when pressure is too low. Fix the root cause before fitting new tires, or the next set will wear the same way.

Tread Depth Calculator showing 4.2 mm summer tire at 59% wear with uneven wear alert

At 15,000 km per year and the standard wear rate of 6,500 km per mm, that 4.2 mm tire has about 7,800 km left to the recommended 3.0 mm threshold. Six months. Not urgent, but close enough to start watching prices.

Is your tread still safe?

Check your measurement against the wear table:

30 MPG is not 30 MPG

Someone recommends a car and says "it gets 30 miles per gallon." If they are American, that means 7.84 L/100 km. If they are British, it means 6.53 L/100 km. Same number, different gallon, 20% gap in actual fuel consumption.

The US gallon holds 3.785 liters. The UK Imperial gallon holds 4.546 liters. Since MPG measures how far you travel on one gallon, the bigger UK gallon naturally produces a higher number. A car that gets 30 MPG in America gets 36 MPG in Britain. Not because British cars are more efficient - because British gallons are larger.

The converter handles both. Pick your direction (MPG to L/100 km or the reverse), select US or UK gallon, enter the number. You get all three formats instantly: L/100 km, US MPG, UK MPG. Plus km/L for Japanese specs and cost estimates.

MPG to L/100km Converter showing 30 US MPG equals 7.84 L/100 km and 36.0 UK MPG

There is a deeper quirk here that most people miss. MPG and L/100 km do not scale the same way. Improving from 10 to 20 MPG saves far more fuel than improving from 30 to 40 MPG - even though both jumps are "10 MPG." In liters: 10 to 20 MPG saves 11.8 L/100 km. 30 to 40 MPG saves only 1.9 L/100 km. Duke University researchers called this the "MPG illusion" - people consistently overvalue MPG improvements at the top of the scale and undervalue them at the bottom.

The practical takeaway: swapping a 14 MPG pickup for a 24 MPG sedan saves more fuel per year than swapping a 30 MPG sedan for a 50 MPG hybrid. Over the same distance.

Quick MPG conversions

Five rules for winter driving numbers

1. WLTP is a summer number. Rated range assumes 20-25C. Every degree below 15C costs you range. At -10C, expect 35-55% less depending on heating and route.

2. The heater is the biggest drain. Not the cold battery - the heater. A PTC heater at city speeds can double your consumption. Heat pump reduces this by half. Check your spec sheet.

3. Precondition from the plug. Five minutes of wall-powered warming saves 5-10% of battery range and gives you a warm cabin from the start. No downside.

4. Measure tread in the groove, not on the block. The deepest grooves drain water. Measure there. If center and edge differ by more than 1 mm, check alignment and tire pressure before buying new tires.

5. Always check which gallon. US and UK MPG differ by 20%. A "55 MPG" UK review is only 45.8 MPG in US terms. The converter shows both side by side.

Tools discussed in this article

EV Winter Range Calculator - Calculate real EV range in cold weather with temperature, heating type, preconditioning, tire and route penalties. Based on AAA and Geotab research data.

Tread Depth Calculator - Measure tire tread depth and get wear percentage, remaining kilometers, months to replacement and uneven wear alerts for summer, winter and all-season tires.

MPG to L/100km Converter - Convert fuel economy between US MPG, UK Imperial MPG and L/100 km. Includes km/L, cost per 100 km and a reference table from 10 to 60 MPG.

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