How fast was the vehicle going before it braked? Enter the skid length, road surface, and grade to estimate the minimum speed at the start of the skid.
Skid-to-Stop SpeedLive
accident reconstruction
Minimum speed at start of skid
43mph
Controls
Presets
The minimum speed at the start of a skid follows v = √(30·D·f·n), where D is skid distance, f the surface drag factor, and n braking efficiency. Uphill grade adds to f, downhill subtracts. Estimation aid — a formal reconstruction requires scene measurement and a drag-factor test.
Reading this result: A 90 ft skid on this surface implies a minimum starting speed near 43 mph — the true speed is at least this, since braking before the skid is not counted.
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How it works
Accident reconstruction uses the skid-to-stop equation v = √(30·D·f·n), where D is skid distance in feet, f the surface drag factor, and n braking efficiency. Grade adjusts the effective drag factor. This is an estimation aid for training and preliminary analysis — a court-admissible reconstruction requires scene measurement and a measured drag factor.
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The math, the assumptions, real-world uses, or a code translation — explained for this exact simulation.
Is this skid to stop speed calculator tool really free?▾
Yes. Skid-to-Stop Speed runs entirely in your browser using your device's own compute, so local use is free forever. You only pay Compute Tokens if you scale a job to the cloud.
Do I need to install anything?▾
No. Everything runs client-side in a modern browser — no downloads, no license, no account required to start.
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How accurate are the results?▾
The solver uses established numerical methods, but results are for research and educational purposes and should be validated against experiment or professional review before you rely on them.