As a general rule, die cushion rated tonnage should be between 10 and 20% of the rated press tonnage. There are two different ways to decide what tonnage die cushion should have:
It is recommended that short run stamping houses and job shops choose cushions with higher tonnage (15-20%) to be suitable for any job that might be run.
When the final product is known, the die cushion tonnage can be computed from its known geometry and material. This approach is recommended when the press will be run only for one kind of product or range of products that require similar die cushion tonnage. Please refer to Tonnage for Drawing Shells page for example of how to calculate required R.H.F. (ring holding force).
Rated die cushion tonnage is calculated from the following formula:

Die Cushion Tonnage = Rated Die Cushion Pressure / Die Cushion Area

Rated Die Cushion Presssure is the maximum pressure that the die cushion that be run at. For C, D, MC, and MD models it is 100 psi, while HC, HD and HMC are run at 200 psi maximum.
Die Cushion Area is the cross-sectional area of die cushion. Each die cushion model identifies its diameter, so D10 die cushion has the chamber of 10" diameter. In case of MC, MD and HMC die cushions, their area calculated from cushion diameter has to be doubled as these cushions have 2 air chambers.
Die cushions can be run at pressures lower than their maximum pressure, thus delivering less tonnage/ring holding force. To calculate their tonnage at any given pressure, in Die Cushion Tonnage formula subsitute Rated Die Cushion Pressure with it or use tonnage calculator below.