Calculate Minimum Safety Distance for Cobots

A free browser-based tool for computing the minimum protective separation distance (S) in collaborative robot cells. Based on ISO 13855 (safeguard positioning) and ISO/TS 15066 speed & separation monitoring. Enter approach speed K, robot and sensor stopping times, and intrusion distance C — or compute C automatically from your safeguard detection capability.

How to Use the Cobot Safety Distance Calculator

Select the approach speed K

Choose 2000 mm/s for whole-body approach or 1600 mm/s for hand/arm. Select "Custom" to enter a project-specific value.

Enter stopping times Tr and Ts

Tr is the robot's stopping time from safeguard trip to rest. Ts is the sensor and control response time. T = Tr + Ts is computed automatically.

Set the intrusion distance C

Enter C directly in mm, or switch to "Compute from d" and enter your safeguard detection capability d (14 < d ≤ 40 mm). The tool applies ISO 13855: C = 8 × (d − 14).

Read the result

The minimum protective separation distance S is shown in mm and metres, with the full formula breakdown K × T + C displayed.

Compute ISO 13855 protective separation in seconds — enter K, T, and C

⚠️ Engineering estimate for planning only. A formal risk assessment using the complete standards (ISO 13855, ISO/TS 15066, ISO 10218-1/-2) must be performed by a qualified safety engineer before deploying any collaborative robot cell.

Quick Presets

Parameters

K — Approach speed of the body or hand toward the hazard

mm/s

Tr — Robot stopping time (Tr)

Ts — Sensor + control response time (Ts)

T — Total system stopping time (T = Tr + Ts, auto-computed)

C — Intrusion / penetration distance (C)

ISO 13855 formula for hand-detection devices: C = 8 × (d − 14), 14 < d ≤ 40 mm

Features

ISO 13855 formula S = K × T + C with full parameter breakdown Approach speed presets: 2000 mm/s (whole-body) and 1600 mm/s (hand/arm) Auto-compute intrusion distance C from detection capability d (mm) Displays S in both mm and metres with a clear formula trace Quick presets for pick-and-place, light-curtain, and area-scanner cells Runs entirely in the browser — no installation required

FAQ

What is the ISO 13855 separation distance formula?

ISO 13855 defines S = (K × T) + C, where K is the approach speed constant (mm/s), T is the total system stopping time (s), and C is the intrusion distance (mm). The result S is the minimum distance to position a safeguarding device from the hazard zone.

What is the difference between ISO 13855 and ISO/TS 15066 SSM?

ISO 13855 provides the general positioning principle. ISO/TS 15066 Speed & Separation Monitoring (SSM) extends it by adding the operator and robot travel distances during the stopping process, plus position uncertainty values Zd and Zr. This tool computes the baseline ISO 13855 form. For full SSM, consult your system integrator.

Which approach speed K should I use?

ISO 13855 Table 1 recommends 2000 mm/s for whole-body detection scenarios and 1600 mm/s for hand and arm detection. Use "Custom" if your risk assessment specifies a different value.

How is C calculated from detection capability d?

For hand-detection devices where 14 mm < d ≤ 40 mm, ISO 13855 gives C = 8 × (d − 14), with a minimum of 0. Switch to the "Compute from d" tab and enter your safeguard's detection capability in mm.

What happens when detection capability d is above 40 mm?

Above 40 mm the safeguard detects the whole body rather than a hand, so the C = 8 × (d − 14) formula no longer applies. ISO 13855 fixes the intrusion distance at C = 850 mm, and the calculator switches to this value automatically.

Is this calculator a substitute for a formal risk assessment?

No. This tool provides a planning estimate only. A qualified safety engineer must perform a complete risk assessment per ISO 13855, ISO/TS 15066, and ISO 10218-1/-2 before deploying any collaborative robot system.

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Published 18 May 2026 Updated 29 May 2026