Comparable worktop heights for table size marks according to BS EN 1729-part 1:    Size Mark 3 - 590mm high Size Mark 4 - 640mm high Size Mark 5 - 710mm high  Size Mark 6 - 750mm high (10mm tolerance allowed either way)   Comparable seat heights for chair size marks according to BS EN 1729-part 1:   Size Mark 3 - 350mm high Size Mark 4 - 380mm high Size Mark 5 - 430mm high Size Mark 6 - 450mm high (10mm tolerance allowed either way)