Cable Railing Screw & Lag Length Selector
Choose the current stair fitting attachment for metal posts, wood posts, or wall framing, then calculate the run kits required for your cable rows.
Match the stair fitting attachment to the post
Choose the post material and connection condition. We will show the corresponding current screw or lag option and calculate the number of stair run kits.
2.25 in x 1/4-20 button-head screw
Select this option for a standard 2 in thick metal post.
Metal posts | stair or ramp run11 cable rows shown
Confirm that the post is actually 2 in thick before selecting the screw. Choose the finish and cable length on the product page.
Screw and lag options by connection condition
These choices reflect the attachment options currently listed on our stair run kit product pages. Always confirm the selected variant before ordering.
Count one kit for every cable row in every section
Our current wood- and metal-post stair kits each include two stair fitting assemblies and one pre-cut cable strand.
Count stair sections
Each corner, end post, or transition to a level run ends the current cable path and starts another section.
Count cable rows
One kit covers one cable row across one termination-to-termination stair or ramp section.
Multiply the two counts
Two stair sections with eleven cable rows require twenty-two stair run kits and forty-four fitting assemblies.
The selector matches listed product options; it does not verify post-wall thickness, thread condition, framing location, wall buildup, or structural suitability. Measure the actual connection and follow the current product instructions.
Cable railing screw and lag questions
Use these answers for preliminary product selection, then confirm the product variant and installation instructions for the actual post condition.
Which screw is listed for a 2 inch metal post?
Our current Stair Run Kit for Metal Posts lists a 2.25 inch x 1/4-20 button-head screw for a standard 2 inch thick metal post.
Which screw is listed for a 1.5 inch metal post?
Our current metal-post stair kit lists a 1.75 inch x 1/4-20 button-head screw for a standard 1.5 inch thick metal post.
When is the 0.625 inch set screw used?
The current metal-post stair kit lists the 0.625 inch x 1/4-20 set screw for a post with a compatible pre-tapped 1/4-20 hole. The product page notes that this option can suit corner posts where several cables attach.
Which lag length is used for a wood post?
Our current Stair Run Kit for Wood Posts lists the 1.5 inch lag screw as the standard option for attaching directly to a wood post.
Which lag length is used for a wall attachment?
The current wood-post stair kit lists the 3.5 inch lag screw for wall attachments intended to pass through drywall, sheathing, or siding and reach internal framing. Verify the actual wall buildup and framing before installation.
How many stair run kits do I need?
Multiply the number of cable rows by the number of independent stair or ramp sections. Each current stair run kit includes two stair fitting assemblies and one pre-cut cable strand for one cable row.
Can I use this selector for level cable runs?
No. This page is specifically for the attachment choices listed with our stair or ramp fitting kits. Use the level-run product page and its current instructions for level cable sections.
Turn the attachment choice into a complete railing plan
Draw the level and stair sections, select post materials, and generate a project quantity estimate.