What weight capacity do I actually need in a workbench?

For light DIY, hobby electronics, and household repairs, 300–500 lbs is plenty. For automotive work, woodworking with hand tools, or supporting a benchtop drill press or vise, look at 1,500–2,000 lbs of rated capacity and a hardwood (rubberwood, beech, or maple) top rather than particleboard. Note that advertised capacities assume an evenly distributed static load, not impact.