Threads are the standard metric coarse(most common).
M4 x 0.7mm pitch; thread diameter 4mm; spanner size 7mm.
M5 x 0.8mm pitch; thread diameter 5mm; spanner size 8mm.
M6 x 1.0mm pitch; thread diameter 6mm; spanner size 10mm.
M8 x 1.25mm pitch; thread diameter 8mm; spanner size 13mm.
M10 x 1.50mm pitch; thread diameter 10mm; spanner size 17mm.
M12 x 1.75mm pitch; thread diameter 12mm; spanner size 19mm.
M14 x 2.00mm pitch; thread diameter 14mm; spanner size 22mm.
M16 x 2.00mm pitch; thread diameter 16mm; spanner size 24mm.
M20 x 2.50mm pitch; thread diameter 20mm; spanner size 30mm.