# Thread: Method to measure back post angle?

1. ## Method to measure back post angle?

Is there an easier formula to measure the back post angle than the one provided by TiLite?

“SEAT BACK ANGLE - Measure angle from front of back post to floor. 90° will be perpendicular to the floor. To approximate the angle from the back post to the seat, subtract 2 degrees from measurement G for every 1/2” of dump.”

Or maybe this is the best method and I just need a different explanation of it and would I need something other than a tape measure?

2. You could place the chair on a level floor with its back close to a vertical wall, and take three measurements: top of backrest to wall (TBW), bottom of backrest to wall (BBW), top to bottom of backrest (TBB), then use trigonometry as follows:

Backrest Angle = ARCTAN(TBB/(TBW-BBW)).

For example my chair's measurements with its back to the wall are
TBW = 10.75", BBW = 10.5", TBB = 11".
ARCTAN(11/(10.75-10.5)) =
ARCTAN(11/0.25) =
ARCTAN(44) = 88.7 degrees (leans forward just a bit).

Be aware accuracy of the measurements greatly affects the result. The measurements to the wall need to be horizontal and taken from the same relative place on the backrest (e.g., back edge of backrest frame). And the TBB is vertical from the measurement points of the TBW to BBW. That said, I took my measurements by eye, but I spent years in the trades measuring and using a level.

When you're done calculating, look at your chair from the side to see if your result makes sense.

3. Thank you Chasmengr for your method. Unfortunately, I could not use it since math is not my strong suit nor my assistant's. Another DME says he has a measuring tool and he will bring it by next week. I'll keep you updated. My plan is to order a ZR with a fixed / welded back so the figuring out the back post angle is crucial.

4. ## iphone level app

if you have an iphone, there is a level app, that will tell you the angle.

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