Holding force refers to the force that can be exerted by a suction cup to grip a workpiece. It is calculated by multiplying the pressure difference by the effective suction area of the suction cup (F = Δp x A). The holding force of a suction cup is thus influenced by underpressure and the suction area. It is a theoretical value, specified without safety factors. It is usual to state the holding force of a suction cup with a relative vacuum of 60%.