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Metric-to-Imperial Thread Conversion Tables.

Precision is a cornerstone in engineering, where the exact dimensions of components like screws can significantly impact the outcome.

Navigating between metric thread and imperial thread measurements often presents challenges, especially when selecting high-precision screws for specific applications. 

Our imperial-to-metric conversion chart provides engineers with an essential resource for accurate metric-to-imperial thread conversions, ensuring you find the perfect match for your needs, or finally figure out exactly what that odd screw actually is.

Interchanging metric and imperial threaded fasteners involves more than just matching sizes; it requires careful consideration of differences in major diameters and thread pitches. By utilising our metric-to-imperial thread conversion charts, you can confidently bridge the gap between these measurement systems and maintain the integrity of your assemblies.

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Metric-to-Imperial Major Diameters

The major diameter is the external diameter of the screw thread, and matching this dimension is vital for component compatibility. Our major diameter conversion chart offers precise equivalents between metric and imperial measurements, simplifying the process of finding suitable fasteners.

Imperial Thread Size Major Diameter (Inch) Major Diameter (MM) Metric Thread Size
- 0.0394 1.0000 M1
- 0.0433 1.1000 M1.1
- 0.0472 1.2000 M1.2
- 0.0551 1.4000 M1.4
#0 0.0600 1.5240 -
- 0.0630 1.6000 M1.6
- 0.0709 1.8000 M1.8
#1 0.0730 1.8542 -
- 0.0787 2.0000 M2
#2 0.0860 2.1844 -
- 0.0866 2.2000 M2.2
- 0.0984 2.5000 M2.5
#3 0.0990 2.5146 -
#4 0.1120 2.8448 -
- 0.1181 3.0000 M3
#5 0.1250 3.1750 -
- 0.1378 3.5000 M3.5
#6 0.1380 3.5052 -
- 0.1575 4.0000 M4
#8 0.1640 4.1656 -
- 0.1772 4.5000 M4.5
#10 0.1900 4.8260 -
- 0.1969 5.0000 M5
#12 0.2160 5.4864 -
- 0.2362 6.0000 M6
1/4" 0.2500 6.3500 -
- 0.2756 7.0000 M7
5/16" 0.3125 7.9502 -
- 0.3150 8.0000 M8
- 0.3543 9.0000 M9
3/8" 0.3750 9.5250 -
- 0.3937 10.0000 M10
- 0.4331 11.0000 M11
7/16" 0.4375 11.1252 -
- 0.4724 12.0000 M12
1/2" 0.5000 12.7000 -
- 0.5512 14.0000 M14
9/16" 0.5625 14.3002 -
5/8" 0.6250 15.8750 -
- 0.6299 16.0000 M16
- 0.7087 18.0000 M18
3/4" 0.7500 19.0500 -
- 0.7874 20.0000 M20
- 0.8661 22.0000 M22
7/8" 0.8750 22.2250 -
- 0.9449 24.0000 M24
1" 1.0000 25.4000 -
- 1.0630 27.0000 M27
- 1.1811 30.0000 M30

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Metric-to-Imperial Thread Pitch

Thread pitch refers to the distance between threads on a screw, influencing how tightly components are fastened. Coarse pitches have fewer threads per unit length, allowing for quicker assembly, while fine pitches offer more threads for a secure fit. Our thread pitch conversion chart compares metric pitches with imperial pitches, enabling you to select fasteners with similar threading and avoid issues related to mismatched pitches.

Imperial Thread Size

TPI

(Threads Per Inch)

Thread Pitch (Inch) Thread Pitch (MM) Metric Thread Size
- - 0.0098 0.2500 M1
M1.1
M1.2
- - 0.0118 0.3000 M1.4
#0 (UNF) 80 0.0125 0.3175 -
- - 0.0138 0.3500 M1.6
M1.8
#1 (UNF) 72 0.0139 0.3528 -
#1 (UNC)
#2 (UNF)
64 0.0156 0.3969 -
- - 0.0157 0.4000 M2
- - 0.0177 0.4500 M2.2
M2.5
#2 (UNC)
#3 (UNF)
56 0.0179 0.4536 -
- - 0.0197 0.5000 M3
#3 (UNC)
#4 (UNF)
48 0.0208 0.5292 -
#5 (UNF) 44 0.0227 0.5773 -
- - 0.0236 0.6000 M3.5
#4 (UNC)
#5 (UNC)
#6 (UNF)
40 0.0250 0.6350 -
- - 0.0276 0.7000 M4
- - 0.0295 0.7500 M4.5
#8 (UNF) 36 0.0278 0.7056 -
#6 (UNC)
#8 (UNC)
#10 (UNF)
#12 (UNEF)
1/4" (UNEF)
5/16" (UNEF)
3/8" (UNEF)
32 0.0313 0.7938 -
- - 0.0315 0.8000 M5
#12 (UNF)
1/4" (UNF)
7/16" (UNEF)
1/2" (UNEF)
28 0.0357 0.9071 -
- - 0.0394 1.0000 M6
M7
#10 (UNC)
#12 (UNC)
5/16" (UNF)
3/8" (UNF)
9/16" (UNEF)
5/8" (UNEF)
24 0.0417 1.0583 -
- - 0.0492 1.2500 M8
M9
1/4" (UNC)
7/16" (UNF)
1/2" (UNF)
3/4" (UNEF)
7/8" (UNEF)
1" (UNEF)
20 0.0500 1.2700 -
5/16" (UNC)
9/16" (UNF)
5/8" (UNF)
18 0.0556 1.4111 -
- - 0.0591 1.5000 M10
M11
3/8" (UNC)
3/4" (UNF)
16 0.0625 1.5875 -
- - 0.0689 1.7500 M12
7/16" (UNC)
7/8" (UNF)
14 0.0714 1.8143 -
1/2" (UNC) 13 0.0769 1.9538 -
- - 0.0787 2.0000 M16
9/16" (UNC)
1" (UNF)
12 0.0833 2.1167 -
5/8" (UNC) 11 0.0909 2.3091 -
- - 0.0984 2.5000 M18
M20
M22
3/4" (UNC) 10 0.1000 2.5400 -
7/8" (UNC) 9 0.1111 2.8222 -
- - 0.1181 3.0000 M24
M27
1" (UNC) 8 0.1250 3.1750 -
- - 0.1378 3.5000 M30
M33

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Common Metric & Imperial Screw Lengths

Accurate length conversions between metric and imperial units are often necessary to ensure components fit as intended. Our conversion table for common lengths provides straightforward equivalents, allowing you to translate measurements seamlessly. By referring to this chart, you can select screws and other components that meet your exact specifications, enhancing the precision and reliability of your projects. 

Imperial Fractional Length Length (Inch) Length (MM) Metric Length
- 0.0787 2.0000 2mm
- 0.1181 3.0000 3mm
1/8" 0.1250 3.1750 -
5/32" 0.1563 3.9700 -
- 0.1575 4.0000 4mm
3/16" 0.1875 4.7625 -
- 0.1969 5.0000 5mm
7/32" 0.2188 5.5575 -
- 0.2362 6.0000 6mm
1/4" 0.2500 6.3500 -
- 0.2559 6.5000 6.5mm
- 0.2756 7.0000 7mm
9/32" 0.2813 7.1450 -
5/16" 0.3125 7.9375  
- 0.3150 8.0000 8mm
11/32" 0.3438 8.7325 -
3/8" 0.3750 9.5250 -
- 0.3937 10.0000 10mm
- 0.3937 10.0000 10mm
7/16" 0.4375 11.1125 -
- 0.4724 12.0000 12mm
1/2" 0.5000 12.7000 -
- 0.5512 14.0000 14mm
9/16" 0.5625 14.2875 -
- 0.5906 15.0000 15mm
5/8" 0.6250 15.8750 -
- 0.6299 16.0000 16mm
11/16" 0.6875 17.4625 -
- 0.7087 18.0000 18mm
3/4" 0.7500 19.0500 -
- 0.7874 20.0000 20mm
13/16" 0.8125 20.6375 -
- 0.8661 22.0000 22mm
7/8" 0.8750 22.2250 -
15/16" 0.9375 23.8125 -
- 0.9843 25.0000 25mm
1" 1.0000 25.4000 -
- 1.1811 30.0000 30mm
1 1/4" 1.2500 31.7500 -
- 1.3780 35.0000 35mm
1 1/2" 1.5000 38.1000 -
- 1.5748 40.0000 40mm
1 3/4" 1.7500 44.4500 -
- 1.7717 45.0000 45mm
- 1.9685 50.0000 50mm
2" 2.0000 50.8000 -
- 2.1654 55.0000 55mm
2 1/4" 2.2500 57.1500 -
- 2.3622 60.0000 60mm
2 1/2" 2.5000 63.5000 -
- 2.5591 65.0000 65mm
2 3/4" 2.7500 69.8500 -
- 2.7559 70.0000 70mm
- 2.8740 73.0000 73mm
3" 3.0000 76.2000 -
- 3.1496 80.0000 80mm
- 3.3465 85.0000 85mm
3 1/2" 3.5000 88.9000 -
- 3.5433 90.0000 90mm
- 3.7402 95.0000 95mm
- 3.9370 100.0000 100mm
4" 4.0000 101.6000 -
- 4.3307 110.0000 110mm
4 1/2" 4.5000 114.3000 -
- 4.5276 115.0000 115mm
- 4.7244 120.0000 120mm
- 4.9213 125.0000 125mm
5" 5.0000 127.0000 -
- 5.1181 130.0000 130mm
- 5.3150 135.0000 135mm
- 5.9055 150.0000 150mm
6" 6.0000 152.4000 -
- 6.2992 160.0000 160mm
- 6.6929 170.0000 170mm
- 7.0866 180.0000 180mm
- 7.4803 190.0000 190mm
- 7.8740 200.0000 200mm
8" 8.0000 203.2000 -

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