Bolt Size Chart & Wrench Size Table — Metric & Imperial
Complete bolt, screw and wrench size reference: metric and imperial thread sizes, wrench sizes, hex key sizes and torque reference for common fasteners.
Metric coarse-thread bolts (ISO)
| Size | Thread pitch | Wrench size (hex) | Hex key (Allen) | Tap drill (60% thread) |
|---|---|---|---|---|
| M3 | 0.5 mm | 5.5 mm | 2.5 mm | 2.5 mm |
| M4 | 0.7 mm | 7 mm | 3 mm | 3.3 mm |
| M5 | 0.8 mm | 8 mm | 4 mm | 4.2 mm |
| M6 | 1 mm | 10 mm | 5 mm | 5 mm |
| M8 | 1.25 mm | 13 mm | 6 mm | 6.8 mm |
| M10 | 1.5 mm | 17 mm | 8 mm | 8.5 mm |
| M12 | 1.75 mm | 19 mm | 10 mm | 10.2 mm |
| M14 | 2 mm | 22 mm | 12 mm | 12 mm |
| M16 | 2 mm | 24 mm | 14 mm | 14 mm |
| M18 | 2.5 mm | 27 mm | 14 mm | 15.5 mm |
| M20 | 2.5 mm | 30 mm | 17 mm | 17.5 mm |
| M22 | 2.5 mm | 34 mm | 17 mm | 19.5 mm |
| M24 | 3 mm | 36 mm | 19 mm | 21 mm |
| M27 | 3 mm | 41 mm | 19 mm | 24 mm |
| M30 | 3.5 mm | 46 mm | 22 mm | 26.5 mm |
Imperial UNC bolts
| Size | Threads per inch | SAE wrench size | Metric equivalent |
|---|---|---|---|
| #4-40 | 40 | 7/32" | 5.6 mm |
| #6-32 | 32 | 1/4" | 6.4 mm |
| #8-32 | 32 | 5/16" | 7.9 mm |
| #10-24 | 24 | 3/8" | 9.5 mm |
| #12-24 | 24 | 7/16" | 11.1 mm |
| 1/4-20 | 20 | 7/16" | 11.1 mm |
| 5/16-18 | 18 | 1/2" | 12.7 mm |
| 3/8-16 | 16 | 9/16" | 14.3 mm |
| 7/16-14 | 14 | 5/8" | 15.9 mm |
| 1/2-13 | 13 | 3/4" | 19.1 mm |
| 9/16-12 | 12 | 13/16" | 20.6 mm |
| 5/8-11 | 11 | 15/16" | 23.8 mm |
| 3/4-10 | 10 | 1-1/8" | 28.6 mm |
| 7/8-9 | 9 | 1-5/16" | 33.3 mm |
| 1-8 | 8 | 1-1/2" | 38.1 mm |
Frequently Asked Questions
Are these tools free to use?＋
Yes, all calculators and converters on this page are completely free, with no registration or download required.
Are the conversion results accurate?＋
All calculations use standard international conversion factors and are accurate to 6 decimal places where relevant.
Can I use these tools on my phone?＋
Yes, every tool is fully responsive and works on mobile, tablet and desktop browsers.
Do you sell the tools mentioned on these pages?＋
Yes! We are a professional B2B supplier of power tools, hand tools, garden tools and agricultural machinery. Contact us for a factory-direct quote.
All Free Tools
Unit Converter
Convert between metric and imperial units used in the tool industry: length (inch/mm), weight (kg/lb), torque (Nm/ft-lb), power (kW/HP) and more. Free, instant and accurate.
Torque Conversion Calculator
Convert torque values between Newton-meter (Nm), foot-pound (ft-lb), inch-pound (in-lb) and kilogram-force meter (kgf-m). Essential for impact wrenches, torque wrenches and fastener specs.
Power Converter (kW/HP)
Convert power ratings between kilowatt (kW), horsepower (HP), metric horsepower (PS) and watt (W). Perfect for comparing engines, generators and power tools.
Pressure Converter
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Drill Bit Size Converter
Convert and compare drill bit sizes between fractional inches, wire gauge numbers, letter sizes and metric diameters. Includes a complete decimal inch and millimeter chart.
AWG to mm² Wire Gauge Converter
Convert American Wire Gauge (AWG) to square millimeters (mm²) and diameter, with ampacity reference for common applications. Essential for extension cords and power tools.
Cutting Speed & RPM Calculator
Calculate spindle RPM from cutting speed and workpiece diameter for drilling and milling. Includes recommended cutting speeds for common materials.
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Chainsaw Chain Length Calculator
Calculate chainsaw chain length from drive-link count and pitch. Enter your drive links and chain pitch to get the total chain length in inches, cm and mm.
Bolt Torque Chart
Recommended tightening torque for metric coarse-thread bolts by property class (8.8, 10.9, 12.9). Free reference chart for mechanics, engineers and DIY users.
Air Compressor Size Calculator
Select your pneumatic tools to calculate the required CFM and recommended air compressor size. Free tool sizing calculator for workshops, garages and professionals.
Extension Cord Size Chart
Find the right extension cord gauge for your power tools. Enter the amp draw and cord length to get the recommended AWG, with a complete 18–10 AWG reference chart.
CC to HP Converter
Convert engine displacement (cc) to horsepower (HP) and back for small engines: chainsaws, brush cutters, tillers, generators and more. Includes the typical 14–17 cc per HP range.
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Do you sell the tools mentioned on these pages?
Yes! We are a professional B2B supplier of power tools, hand tools, garden tools and agricultural machinery. Contact us for a factory-direct quote.