Which hand speed K does ISO 13855 use?

The standard assumes a 2,000 mm/sec hand approach for normal detection, which is the default here. Only where that gives more than 500 mm may you recalculate at 1,600 mm/sec, and never below 500 mm.

How is C set by the curtain resolution?

For a light curtain the standard gives C = 8 × (d − 14) millimeters, where d is the detection capability, for resolutions up to 40 mm. The 30 mm resolution gives the 128 mm default.

Can a lower multiplier shorten the distance?

Only with a documented risk assessment. Below 1 the multiplier removes the allowance the standard's distance carries, and this page warns. Keep 1 or more for a normal installation.

Is the calculated distance enough on its own?

No. It sets mounting distance only; the risk assessment sets the performance level, resolution, muting and restart logic. OSHA 1910.212 also requires guarding that protects the operator at the point of operation.

Robotics & Automation calculator

Light Curtain Safety Distance Calculator

Find the mounting distance for a light curtain so a hand cannot reach the hazard before the machine stops. It uses hand speed K, the system stopping time, the depth penetration allowance from the curtain resolution, and a margin.

What this calculator does

ISO 13855 mounting distance for a light curtain, from hand approach speed, stopping time, depth penetration allowance and a safety margin.

Formula used

Reaction travel (mm) = hand approach speed K × total stopping time T
Base distance (mm) = reaction travel plus depth penetration allowance C
Curtain distance (mm) = base distance × margin multiplier
Distance added by margin (mm) = curtain distance less base distance

Inputs explained

Hand Approach Speed K: Hand approach speed K, usually 2,000 mm/sec per ISO 13855.
Stopping Time T to a Full Stop: Curtain trip to full machine stop, from a stop-time test.
Depth Penetration Allowance C: Allowance C from the curtain resolution and detection capability.
Applied Margin Multiplier: Scale factor on the base distance; below 1 removes allowance.

How to use the result

Best suited to mounting a curtain at a robot cell entry, checking distance before a stop test, comparing resolutions for one opening.
ISO 13855 allows 1,600 mm/sec only where 2,000 gives over 500 mm, never below 500 mm; this page keeps your K. Whole body access and reach over or under the curtain need their own risk assessment.

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 hand speed K does ISO 13855 use? The standard assumes a 2,000 mm/sec hand approach for normal detection, which is the default here. Only where that gives more than 500 mm may you recalculate at 1,600 mm/sec, and never below 500 mm.
How is C set by the curtain resolution? For a light curtain the standard gives C = 8 × (d − 14) millimeters, where d is the detection capability, for resolutions up to 40 mm. The 30 mm resolution gives the 128 mm default.
Can a lower multiplier shorten the distance? Only with a documented risk assessment. Below 1 the multiplier removes the allowance the standard's distance carries, and this page warns. Keep 1 or more for a normal installation.
Is the calculated distance enough on its own? No. It sets mounting distance only; the risk assessment sets the performance level, resolution, muting and restart logic. OSHA 1910.212 also requires guarding that protects the operator at the point of operation.

Last reviewed 2026-10-01.