ThreadSpec.org

ISO Metric Coarse Thread Chart

All 36 coarse-pitch ISO metric threads from M1 to M68, with pitch, basic diameters, tap drill, clearance hole and tensile stress area. A metric thread written without a pitch, such as M10, means the coarse pitch in this chart.

Diameters in mm. Clearance hole is the ISO 273 medium series.
ThreadPitch (mm)Pitch Ø d2Minor Ø D1Root Ø d3Tap drill (mm)Clearance holeStress area (mm²)ISO 261 choice
M1×0.250.250.8380.7290.6930.751.20.4601st
M1.2×0.250.251.0380.9290.8930.951.40.7321st
M1.4×0.30.31.2051.0751.0321.11.60.9832nd
M1.6×0.350.351.3731.2211.1711.251.81.271st
M1.8×0.350.351.5731.4211.3711.452.11.702nd
M2×0.40.41.7401.5671.5091.62.42.071st
M2.5×0.450.452.2082.0131.9482.052.93.391st
M3×0.50.52.6752.4592.3872.53.45.031st
M3.5×0.60.63.1102.8502.7642.93.96.782nd
M4×0.70.73.5453.2423.1413.34.58.781st
M5×0.80.84.4804.1344.0194.25.514.21st
M6×115.3504.9174.77356.620.11st
M7×116.3505.9175.77367.628.92nd
M8×1.251.257.1886.6476.4666.8936.61st
M9×1.251.258.1887.6477.4667.8—48.13rd
M10×1.51.59.0268.3768.1608.511581st
M12×1.751.7510.86310.1069.85310.213.584.31st
M14×2212.70111.83511.5461215.51152nd
M16×2214.70113.83513.5461417.51571st
M18×2.52.516.37615.29414.93315.5201922nd
M20×2.52.518.37617.29416.93317.5222451st
M22×2.52.520.37619.29418.93319.5243032nd
M24×3322.05120.75220.31921263531st
M27×3325.05123.75223.31924304592nd
M30×3.53.527.72726.21125.70626.5335611st
M33×3.53.530.72729.21128.70629.5366942nd
M36×4433.40231.67031.09332398171st
M39×4436.40234.67034.09335429762nd
M42×4.54.539.07737.12936.47937.54511201st
M45×4.54.542.07740.12939.47940.54813102nd
M48×5544.75242.58741.866435214701st
M52×5548.75246.58745.866475617602nd
M56×5.55.552.42850.04649.25250.56220301st
M60×5.55.556.42854.04653.25254.56623602nd
M64×6660.10357.50556.639587026801st
M68×6664.10361.50560.639627430602nd

Finer pitches on the same diameters are in the metric fine thread chart.

How pitch grows with diameter

123456M1M2M3M5M8M12M20M36M68Nominal diameter (mm, log scale)Pitch (mm)M1×0.25: pitch 0.25 mmM1.2×0.25: pitch 0.25 mmM1.4×0.3: pitch 0.3 mmM1.6×0.35: pitch 0.35 mmM1.8×0.35: pitch 0.35 mmM2×0.4: pitch 0.4 mmM2.5×0.45: pitch 0.45 mmM3×0.5: pitch 0.5 mmM3.5×0.6: pitch 0.6 mmM4×0.7: pitch 0.7 mmM5×0.8: pitch 0.8 mmM6×1: pitch 1 mmM7×1: pitch 1 mmM8×1.25: pitch 1.25 mmM9×1.25: pitch 1.25 mmM10×1.5: pitch 1.5 mmM12×1.75: pitch 1.75 mmM14×2: pitch 2 mmM16×2: pitch 2 mmM18×2.5: pitch 2.5 mmM20×2.5: pitch 2.5 mmM22×2.5: pitch 2.5 mmM24×3: pitch 3 mmM27×3: pitch 3 mmM30×3.5: pitch 3.5 mmM33×3.5: pitch 3.5 mmM36×4: pitch 4 mmM39×4: pitch 4 mmM42×4.5: pitch 4.5 mmM45×4.5: pitch 4.5 mmM48×5: pitch 5 mmM52×5: pitch 5 mmM56×5.5: pitch 5.5 mmM60×5.5: pitch 5.5 mmM64×6: pitch 6 mmM68×6: pitch 6 mmM3×0.35: pitch 0.35 mmM4×0.5: pitch 0.5 mmM5×0.5: pitch 0.5 mmM6×0.75: pitch 0.75 mmM7×0.75: pitch 0.75 mmM8×0.75: pitch 0.75 mmM8×1: pitch 1 mmM9×1: pitch 1 mmM10×0.75: pitch 0.75 mmM10×1: pitch 1 mmM10×1.25: pitch 1.25 mmM12×1: pitch 1 mmM12×1.25: pitch 1.25 mmM12×1.5: pitch 1.5 mmM14×1: pitch 1 mmM14×1.25: pitch 1.25 mmM14×1.5: pitch 1.5 mmM16×1: pitch 1 mmM16×1.25: pitch 1.25 mmM16×1.5: pitch 1.5 mmM18×1: pitch 1 mmM18×1.5: pitch 1.5 mmM18×2: pitch 2 mmM20×1: pitch 1 mmM20×1.5: pitch 1.5 mmM20×2: pitch 2 mmM22×1: pitch 1 mmM22×1.5: pitch 1.5 mmM22×2: pitch 2 mmM24×1: pitch 1 mmM24×1.5: pitch 1.5 mmM24×2: pitch 2 mmM27×1: pitch 1 mmM27×1.5: pitch 1.5 mmM27×2: pitch 2 mmM30×1: pitch 1 mmM30×1.5: pitch 1.5 mmM30×2: pitch 2 mmM33×1.5: pitch 1.5 mmM33×2: pitch 2 mmM33×3: pitch 3 mmM36×1.5: pitch 1.5 mmM36×2: pitch 2 mmM36×3: pitch 3 mmM39×1.5: pitch 1.5 mmM39×2: pitch 2 mmM39×3: pitch 3 mmM42×1.5: pitch 1.5 mmM42×2: pitch 2 mmM42×3: pitch 3 mmM45×1.5: pitch 1.5 mmM45×2: pitch 2 mmM45×3: pitch 3 mmM48×1.5: pitch 1.5 mmM48×2: pitch 2 mmM48×3: pitch 3 mmCoarse pitchFine pitches
Each diameter has one coarse pitch (green, joined) and up to three fine pitches (orange). Hover or tap a point for the thread.

The coarse pitch is not a fixed fraction of the diameter. It is about a quarter of the diameter at M1, a seventh at M10 and less than a tenth at M64, so small coarse threads are proportionally much deeper than large ones.

Reading the chart

Pitch diameter d2 is where the thread ridge and the groove are equally wide; it is the diameter that decides whether a nut and bolt fit. Minor diameter D1 is the basic bore of the nut thread and the lower limit for a tapped hole. Root diameter d3 is the bottom of the bolt thread with its rounded root, used for strength calculations.

ISO 261 choice ranks the diameters. First-choice sizes are the ones to design with; second and third choice sizes (M7, M9, M14, M18, M22 and so on) are standard but stocked less widely.

All values are basic sizes, before tolerances. Each thread page gives the 6g and 6H limits, a range of usable tap drills and proof loads by property class.

Common questions

What is the tap drill for M8?

The tap drill for M8×1.25 is 6.8 mm. The rule is diameter minus pitch, 8 − 1.25 = 6.75 mm, rounded to the stocked 6.8 mm drill. It leaves about 74% thread.

Is M10 the same as M10×1.5?

Yes. When no pitch is given the coarse pitch is meant, and the coarse pitch of M10 is 1.5 mm. M10×1.25 and M10×1 are fine-pitch threads and need different taps and nuts.

Why is there no clearance hole for M9?

ISO 273 does not list the 9 mm size. M9 is a third-choice diameter that new designs avoid.

Other charts and tools

Sources: ISO 261 (pitches and choice), ISO 724 (basic dimensions), ISO 273 (clearance holes), ISO 898-1 (stress areas) and tap drill tables based on ISO 2306. How this site checks its data. Last reviewed 29 September 2026.