Stopping Distance Calculator

Reaction + braking · surface friction

Quick Answer

Stopping Distance Calculator: Reaction + braking · surface friction. Stopping Distance Calculator uses standard science & engineering formulas to compute accurate results instantly.

Speed (km/h)

km/h

Road surface

Reaction time

Total stopping distance

35.6 m

Reaction 16.7 m + braking 18.9 m

Reaction distance16.7 m

Braking distance18.9 m

Total35.6 m

Friction μ0.75

Distance by speed (current conditions)

Speed	Reaction	Braking	Total
20 km/h	5.6 m	2.1 m	7.7 m
30 km/h	8.3 m	4.7 m	13.1 m
40 km/h	11.1 m	8.4 m	19.5 m
50 km/h	13.9 m	13.1 m	27.0 m
60 km/h	16.7 m	18.9 m	35.6 m
80 km/h	22.2 m	33.6 m	55.8 m
100 km/h	27.8 m	52.5 m	80.3 m
120 km/h	33.3 m	75.6 m	108.9 m

Braking distance grows with the SQUARE of speed: double the speed = 4× the braking distance. On wet roads (μ≈0.45) everything nearly doubles; on ice (μ≈0.1) it is ~7×. The "2-second rule" (4s in rain) keeps your following distance ≥ reaction distance — but only braking distance scales with v², so higher speeds need much bigger gaps.

Calculation steps

1Reaction distance = v/3.6 × t = 16.67 m/s × 1 s = 16.7 m
2Braking distance = v²/(254μ) = 60²/(254×0.75) = 18.9 m
3Total stopping distance = 16.7 + 18.9 = 35.6 m

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How to Use

Enter known quantities: fill values and confirm units in the Stopping Distance Calculator.
Instant solution: unknowns solve live with the formula shown transparently.
Use constant/material tables: standard physical constants and material data are listed on this page.
Compare conditions: change inputs to compare scenarios.

Key Points

Stopping Distance Calculator is a free online science & engineering tool — open and use, no sign-up.
All calculations run locally in your browser; your data never leaves the device.
Key capability: Reaction + braking · surface friction.
Results come with formulas and reference tables so you can verify every number.

Formula & How It Works

Stopping Distance Calculator formula

Stopping Distance Calculator uses standard science & engineering formulas to compute accurate results instantly.

FAQ

How do I use the Stopping Distance Calculator?

Open the page and fill in the input fields — results update automatically. Reaction + braking · surface friction.

Are the results accurate?

Yes. Standard formulas and conversion factors are used and verified.

Is it free? Do I need to sign up?

Completely free. No registration, login or download required.

Does it work on mobile?

Yes. The responsive design works on phones, tablets and desktops.

Is my data saved?

No. Everything runs locally in your browser.

Related Guides

Source & Updates

Based on CODATA recommended constants and standard physics formulas. Last updated: 2025-07

Last updated: 2026-08-05

Formulas and content on this page are reviewed by the YiJianSuan team. For reference only — official sources prevail.

Cite this page: YiJianSuan. Stopping Distance Calculator[EB/OL]. https://www.yijiansuan.com/en/c/science/stopping-distance

Results provided by this tool are for reference only and do not constitute professional advice.

Distance by speed (current conditions)

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How to Use

Key Points

Formula & How It Works

FAQ

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Source & Updates

Distance by speed (current conditions)