Why can my gripper not reach a point inside the rated reach?

Rated reach ends at the wrist center, not the tool center point. A downward tool lifts the wrist center above the point, and a point well above or below J2 shortens the horizontal reach.

Where do I find the J1 to J2 offset?

On the dimensioned side view of the datasheet's operating space drawing: the horizontal distance from the J1 rotation axis to the J2 axis. Enter 0 if the J2 axis crosses J1.

How much reach margin should a layout keep?

Use your own layout rule; this page gives geometry, not a standard minimum. Cover base placement tolerance, fixture adjustment and the wrist angle the point needs.

Does a riser or a seventh-axis rail change the answer?

Yes. A riser raises J2, so measure the point's height from the new J2 height. A rail moves J1, so measure from the rail position nearest the point.

Robotics & Automation calculator

Robot Reach Margin Calculator

Check, while placing the robot base, whether a six-axis arm reaches your farthest point with the tool fitted. You need the datasheet reach and J1 to J2 offset, the point's position and the tool's offsets.

What this calculator does

How far inside full stretch a robot's wrist center sits at your farthest tool point, allowing for tool length and height.

Formula used

Wrist center distance from J1 = far point distance − tool reach
Wrist center height above J2 = far point height + tool drop
J2 to wrist center = √((wrist center distance − J1 to J2 offset)² + wrist center height²)
Reach margin (mm) = rated reach − J1 to J2 offset − J2 to wrist center
Arm extension (%) = J2 to wrist center ÷ (rated reach − J1 to J2 offset) × 100

Inputs explained

Rated Reach: Datasheet max reach, J1 axis to the wrist center.
J1 to J2 Offset: Horizontal J1 axis to J2 axis distance on the datasheet drawing.
Far Point Distance From J1: Horizontal J1 axis to farthest tool center point, from the layout.
Far Point Height Above J2: Tool center point height minus J2 axis height; negative below.
Tool Drop Below Wrist Center: Wrist center down to tool center point, J5 to flange included.
Tool Reach Beyond Wrist Center: Wrist center out to tool center point, J5 to flange included.

How to use the result

Best suited to placing the robot base in a new layout, checking a far pallet corner or conveyor edge, loading a machine with a horizontal gripper.
Joint limits, rear interference zones and wrist orientation are not checked; confirm the pose in simulation. Arms rated to the flange end, as some cobots are, read high by about the J5 to flange length.

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

Why can my gripper not reach a point inside the rated reach? Rated reach ends at the wrist center, not the tool center point. A downward tool lifts the wrist center above the point, and a point well above or below J2 shortens the horizontal reach.
Where do I find the J1 to J2 offset? On the dimensioned side view of the datasheet's operating space drawing: the horizontal distance from the J1 rotation axis to the J2 axis. Enter 0 if the J2 axis crosses J1.
How much reach margin should a layout keep? Use your own layout rule; this page gives geometry, not a standard minimum. Cover base placement tolerance, fixture adjustment and the wrist angle the point needs.
Does a riser or a seventh-axis rail change the answer? Yes. A riser raises J2, so measure the point's height from the new J2 height. A rail moves J1, so measure from the rail position nearest the point.

Last reviewed 2026-10-01.