How this calculator works
Comparing how much tread has worn away against how far you've driven gives a wear rate in millimeters per kilometer. Dividing the tread you have left above the TWI wear limit by that rate tells you roughly how many more kilometers the tire has before it needs replacing.
More detail
Why the TWI wear limit matters
Below 1.6 mm of tread, a tire loses most of its ability to channel water away from the contact patch, sharply increasing hydroplaning risk in rain — which is why it's treated as a hard replacement line rather than a soft suggestion. This calculator flags a tire already at or under that depth instead of showing a misleading distance number.
Check more than one spot. Wear is rarely perfectly even — check tread depth at the outer, center, and inner parts of the tire. Faster wear on one side usually points to an alignment or tire-pressure problem worth fixing before it shortens the tire's life further.
Frequently asked questions
Current depth 5 mm, 30,000 km driven, new depth 8 mm — how much distance is left?
Wear rate is (8 − 5) ÷ 30,000 = 0.0001 mm/km, which the calculator shows as 1.00 mm per 10,000 km. Tread remaining above the TWI limit is 3.4 mm, giving roughly 34,000 km left.
What happens if current depth is already at or below 1.6 mm?
The calculator shows the tire needs replacing now rather than a distance figure, since there's no safety margin left to spend.
Does uneven wear affect this estimate?
Yes — this calculator assumes the wear rate you measured stays constant, but tires that wear unevenly (often from misalignment or wrong pressure) can hit the TWI wear limit on one edge well before the average depth would suggest.