How do you calculate robot safety distance?

Multiply the approach speed K by the total system stopping time T, add the intrusion distance C, then apply your safety margin. The base distance is (K x T) + C; here (1600 x 0.35) + 128 = 688, and a 1.2x margin brings it to the required distance shown.

What is the stopping time T in the formula?

T is the overall system response: the time from the sensor detecting an intrusion until the robot and all hazardous motion come to rest, including control-system latency and the robot's own stopping distance in time. Use a measured stop-time from your safety controller, not the robot spec sheet alone.

Why include an intrusion distance C?

C accounts for a hand or body reaching toward the hazard before the sensing field is broken, or reaching over/through a guard. For whole-body detection it can be substantial, so it is added on top of the speed-times-time term to keep the barrier honest.

What approach speed K should I use?

ISO 13855 uses 1600 mm/s for a walking/reaching approach and 2000 mm/s for hand movement in some cases. Using too low a K shrinks the distance and creates a hazard, so use the standard's mandated value for your access type.

Should I add a safety margin on top of the standard?

The core distance comes from the standard, but many integrators apply a multiplier (here 1.2x) to cover measurement uncertainty in stop time, drift as the robot ages, and installation tolerance. It is a deliberate conservatism, not a substitute for correct inputs.

Does a faster robot always need more distance?

Not directly. The distance depends on human approach speed K and system stop time T, not robot speed itself. But a faster or heavier robot usually has a longer stop time T, which does increase the required distance through that term.

Robotics & Automation calculator

Robot Safety Distance Calculator

Robot safety distance is the minimum separation a fixed guard or presence-sensing device must sit from a robot hazard so the robot fully stops before a person can reach it. Machine safety engineers and integrators calculate it to comply with ISO 13855 and ANSI/RIA R15.06 when laying out a workcell. It combines how fast a person approaches, how long the whole system takes to stop, and an allowance for reaching over or through the guard. Get it wrong and you either create a pinch hazard or waste valuable floor space around the cell.

What this calculator does

Estimate ISO 13855 style safety distance between a moving robot and a presence-sensing device from approach speed, system stopping time, intrusion distance, and a margin.
Use it during cell layout to size guarding distance to a light curtain, scanner, or safety mat before commissioning, then confirm with a safety stop test.
It multiplies approach speed by total stopping time, adds the intrusion allowance, then applies a safety margin to return the minimum safeguarding distance.

Formula used

Base safety distance = (approach speed K x overall system stopping time T) + intrusion distance C
Required safety distance = base safety distance x safety margin multiplier

Inputs explained

Robot approach/reach speed K:
Total stopping time T (robot + control response):
Reach-past intrusion allowance C:
Applied safety margin multiplier:

How to use the result

Use it when positioning fixed fencing, safety mats, or scanners around a robot during cell design or a safety validation.
This is a planning aid; the governing figures for K, T and C and the correct standard (ISO 13855) must be verified against your validated stop-time measurement and a formal risk assessment before build.

Current U.S. benchmarks

Global copper trades at $13,484 per tonne (IMF via FRED, May 2026), up 41.5% in a year, and U.S. industrial electricity averages 8.66 cents per kWh. Both feed electrified-hardware unit economics.

Common questions

How do you calculate robot safety distance? Multiply the approach speed K by the total system stopping time T, add the intrusion distance C, then apply your safety margin. The base distance is (K x T) + C; here (1600 x 0.35) + 128 = 688, and a 1.2x margin brings it to the required distance shown.
What is the stopping time T in the formula? T is the overall system response: the time from the sensor detecting an intrusion until the robot and all hazardous motion come to rest, including control-system latency and the robot's own stopping distance in time. Use a measured stop-time from your safety controller, not the robot spec sheet alone.
Why include an intrusion distance C? C accounts for a hand or body reaching toward the hazard before the sensing field is broken, or reaching over/through a guard. For whole-body detection it can be substantial, so it is added on top of the speed-times-time term to keep the barrier honest.
What approach speed K should I use? ISO 13855 uses 1600 mm/s for a walking/reaching approach and 2000 mm/s for hand movement in some cases. Using too low a K shrinks the distance and creates a hazard, so use the standard's mandated value for your access type.
Should I add a safety margin on top of the standard? The core distance comes from the standard, but many integrators apply a multiplier (here 1.2x) to cover measurement uncertainty in stop time, drift as the robot ages, and installation tolerance. It is a deliberate conservatism, not a substitute for correct inputs.

Last reviewed 2026-05-12.