Which speed K should I enter for a robot?

Not the robot's speed. K is how fast a person approaches the hazard: ISO 13855 uses 1,600 mm/sec for the body and 2,000 mm/sec for hands and arms. Robot speed and braking belong in the stopping time T.

What belongs in the stopping time T?

Every delay from detection to a full stop: safeguard response, safety controller, robot control and braking. Only a stop-time measurement on the real cell shows the total.

How do I choose the allowance C?

It depends on the safeguard: reach past a detection plane, mesh openings, or the step onto a mat. Use the value your risk assessment fixed; the 128 mm default is a common reach-past figure.

Why is the margin added negative?

Because the entered multiplier is below 1, so the distance shrinks below the base value instead of carrying extra allowance. Treat that as a deliberate derating only when the risk assessment supports it.

Robotics & Automation calculator

Robot Safety Distance Calculator

Find how far a robot must sit from a safeguard so a person cannot reach the hazard before it stops. The ISO 13855 form is approach speed times stopping time plus intrusion allowance, scaled by your margin.

What this calculator does

ISO 13855 safety distance from a moving robot to a safeguard, using approach speed, system stopping time, intrusion allowance and a margin.

Formula used

Reaction travel (mm) = approach speed K × total stopping time T
Base distance (mm) = reaction travel plus intrusion allowance C
Required safety distance (mm) = base distance × safety margin multiplier
Distance added by margin (mm) = required safety distance less base distance

Inputs explained

Approach Speed K: Human body or hand approach speed; ISO 13855 uses 1,600 or 2,000.
Total Stopping Time T: Overall system stopping time T, robot plus control response.
Intrusion Allowance C: Reach-past intrusion allowance C for the detection zone depth.
Safety Margin Multiplier: Multiplier on the base distance; enter 1 or more.

How to use the result

Best suited to sizing a fence gap before commissioning, checking a scanner or mat distance, recording the distance for the risk assessment.
This page covers reach through the safeguard plane; whole body access and stepping over need their own assessment. A measured stop time and a documented risk assessment remain necessary before production.

Current U.S. benchmarks

Global copper trades at $13,543 per tonne (IMF via FRED, Jul 2026), up 38.6% in a year, and U.S. industrial electricity averages 9.77 cents per kWh. Both feed electrified-hardware unit economics.

Common questions

Which speed K should I enter for a robot? Not the robot's speed. K is how fast a person approaches the hazard: ISO 13855 uses 1,600 mm/sec for the body and 2,000 mm/sec for hands and arms. Robot speed and braking belong in the stopping time T.
What belongs in the stopping time T? Every delay from detection to a full stop: safeguard response, safety controller, robot control and braking. Only a stop-time measurement on the real cell shows the total.
How do I choose the allowance C? It depends on the safeguard: reach past a detection plane, mesh openings, or the step onto a mat. Use the value your risk assessment fixed; the 128 mm default is a common reach-past figure.
Why is the margin added negative? Because the entered multiplier is below 1, so the distance shrinks below the base value instead of carrying extra allowance. Treat that as a deliberate derating only when the risk assessment supports it.

Last reviewed 2026-10-01.