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