Sandpaper grit chart: P and CAMI in microns

FEPA P grades, average particle size
P grade	µm
P24	740
P30	622
P36	524
P40	412
P50	326
P60	260
P80	197
P100	156
P120	127
P150	97
P180	78
P220	65
P240	58.5
P280	52.5
P320	46.2
P360	40.5
P400	35
P500	30.2
P600	26
P800	21.8
P1000	18.3
P1200	15.3
P1500	12.7
P2000	9.8

CAMI (US) grades, and the nearest P grade
CAMI	µm	Nearest P
24	715	P24
30	638	P30
36	535	P36
40	428	P40
50	351	P50
60	268	P60
80	192	P80
100	141	P120
120	116	P120
150	93	P150
180	78	P180
220	66	P220
240	53.5	P280
280	43	P360
320	36	P400
360	28.8	P500
400	23.6	P800
500	19.7	P1000
600	16	P1200
800	12.3	P1500
1000	9.3	P2000