Gem cutting: Adjusting the angle - Tangent Ratio Method - Calculate Now

The Critical Angle, or CA for short, is the (too steep) cut angle at the pavilion (usually the one that forms the center point of the cut) where the stone can no longer reflect the light and the reason why you can "see through" some cut gemstones. To prevent this, one must logically change the angle indication on the design chart to an angle above the critical angle (optimally 1.5° higher).

Now you have to adjust the other facets according to this change to keep the complete cut of the stone. Now, if you don't have software like GemCad or GemCut-Studio, you can do this with the tangent ratio method. This calculator makes it easy for the cutter to calculate the correct angles for the optimum cut pattern.

All you have to do is enter in the first field the angle you chose to get above the CA, in the second field you enter the angle that would have been below the CA according to the diagram and was therefore changed, and in the third field you gradually enter the remaining angles that have to be adjusted according to the change.

Info: the simpler the design, the more accurate the result. For more complicated designs, using the tangent ratio method can still produce undesirable results, so using software for complicated designs would be advisable.

The calculator can be checked by entering the same value in the third field as in field number two. the result should then have the same value as in field number one.