What is Thigh Clearance?

Thigh clearance is how much room you need to be able to slide under a table top when sitting in a chair.  In anthropometrics, thigh clearance is is defined as the vertical distance from the surface of the seat to the top of the soft tissue of the thigh at the thickest part.  The thickest part of the thigh when seated is usually within the top third of the upper leg closer to the hip than the knee.

How is Thigh Clearance Measured?

Thigh clearance is measured on a seated subject holding good posture.  The tissue of the thigh needs to be loose and uncompressed.  Calipers or a measuring stick with an arm perpendicular to the measuring stick is used.  The arm is adjusted down until it contacts the top of the thigh, therefore transferring the vertical distance from the seat surface to the top of the thigh to the measuring stick.

What is Thigh Clearance Used For?

Thigh clearance is used to determine the amount of clearance needed between the top of a seat pan or cushion and the bottom of a seated work surface for someone to be able to sit with their legs underneath the work surface.  Thigh clearance is often used in the design of tables and desks, especially when their is some type of custom seating solution used.

Common Adjustments to Thigh Clearance

Since anthropometric measurements are taken on unclothed subjects, adjustments to thigh clearance is often needed for a variety of clothes.  And some adjustments need to be made based on seat construction.

 

For clothed operators 1/4 inch can be added for normal weight clothes worn below the waist, 1 to 1 and 1/2 inch can be added for heavy clothes (like cold weather gear).  

The construction of the seat should be taken into consideration and the compression of the seat cushion should be measured and added to the available clearance between seat height and the bottom of the table.

Thigh Clearance may also be referred to as Thigh Thickness.