What is the metric equivalent of a 10mm socket?

A 10mm socket is already metric. The closest SAE equivalent is 3/8 inch (9.525mm), but it's slightly smaller. For exact fit on metric fasteners, always use the correct metric socket.

What SAE size is closest to 13mm?

The closest SAE size to 13mm is 1/2 inch (12.7mm). It's 0.3mm smaller, which may work in a pinch but isn't recommended for precision work as it can round off bolt heads.

How do I convert foot-pounds to Newton-meters?

To convert foot-pounds (ft-lb) to Newton-meters (Nm), multiply by 1.3558. For example, 100 ft-lb = 135.58 Nm. Our calculator handles this conversion automatically.

What is the difference between UNC and UNF threads?

UNC (Unified National Coarse) has fewer threads per inch and is more common for general use. UNF (Unified National Fine) has more threads per inch, providing stronger clamping but more susceptible to cross-threading. Metric threads use pitch in millimeters instead of threads per inch.

What size socket do I need for lug nuts?

Common lug nut socket sizes vary by vehicle: 17mm, 19mm, 21mm, and 22mm are most common for metric. SAE sizes include 3/4", 13/16", and 7/8". Always verify your specific vehicle's lug nut size before purchasing tools.

Can I use SAE sockets on metric bolts?

While some SAE and metric sizes are close, using the wrong socket can damage bolt heads. For example, 19mm and 3/4" are only 0.05mm apart and can often interchange. However, 14mm and 9/16" (0.36mm difference) should not be interchanged. Use the correct size whenever possible.

What is the most common metric socket size?

The 10mm socket is notoriously the most commonly used (and lost!) metric socket size. Other frequently used metric sizes include 8mm, 12mm, 13mm, 14mm, 17mm, and 19mm.

How do I read metric bolt sizes like M8x1.25?

In "M8x1.25", the M indicates metric, 8 is the nominal diameter in millimeters, and 1.25 is the thread pitch in millimeters. Coarse thread (standard) M8 is 1.25mm pitch, while fine thread M8 is typically 1.0mm pitch.

What torque should I use for wheel lug nuts?

Lug nut torque varies by vehicle, typically 80-100 ft-lb (108-135 Nm) for passenger cars and 90-120 ft-lb (122-163 Nm) for trucks/SUVs. Always consult your vehicle's manual for exact specifications.

What is the difference between Grade 8 and 10.9 bolts?

Grade 8 is SAE standard with 150,000 PSI tensile strength, marked with 6 radial lines. Class 10.9 is metric with similar strength (145,000 PSI minimum), marked with "10.9" on the head. They're roughly equivalent in strength but have different thread specifications.

What is the metric equivalent of a 10mm socket?

A 10mm socket is already metric! The closest SAE equivalent is 3/8 inch (9.525mm), but it's 0.475mm smaller. For precise work on metric fasteners, always use the correct 10mm socket. The 10mm is notorious for being the most commonly used (and lost!) socket in automotive work.

What SAE size is closest to 13mm?

The closest SAE size to 13mm is 1/2 inch (12.7mm), which is 0.3mm smaller. While it may work in a pinch, using the wrong size risks rounding off bolt heads. Always use the correct 13mm socket when possible.

How do I convert foot-pounds to Newton-meters?

To convert foot-pounds (ft-lb) to Newton-meters (Nm), multiply by 1.3558. For example: 100 ft-lb × 1.3558 = 135.58 Nm. For a quick estimate, multiply ft-lb by 1.35.

What is the difference between UNC and UNF threads?

UNC (Unified National Coarse) has fewer threads per inch and is the most common for general use. UNF (Unified National Fine) has more threads per inch, providing better clamping force but is more susceptible to cross-threading. Metric threads use pitch in millimeters (e.g., M8x1.25 = 8mm diameter, 1.25mm between threads).

Can I use SAE sockets on metric bolts?

While some sizes are close (like 19mm and 3/4"), using the wrong socket can damage fasteners. Sizes within 0.1mm can sometimes interchange safely, but anything more risks rounding bolt heads. Our chart shows the exact differences to help you decide.

What torque should I use for lug nuts?

Lug nut torque varies: Compact cars typically need 76-90 ft-lb (103-122 Nm), sedans/SUVs need 80-100 ft-lb (108-135 Nm), and trucks may need 95-120 ft-lb (129-163 Nm). Always check your vehicle's manual and re-torque after 50 miles on new wheels.

What is the most common metric socket size?

The 10mm socket is the most commonly used metric size, followed by 8mm, 12mm, 13mm, 14mm, 17mm, and 19mm. The 10mm is so commonly used (and lost!) that it's become an inside joke among mechanics.

How do I read metric bolt sizes like M8x1.25?

The format is M[diameter]x[pitch]. M8x1.25 means: M = Metric, 8 = 8mm nominal diameter, 1.25 = 1.25mm thread pitch. Standard (coarse) M8 is 1.25mm pitch, while fine thread M8 is 1.0mm pitch.

What is the difference between Grade 8 and 10.9 bolts?

Grade 8 is SAE standard (marked with 6 radial lines) with 150,000 PSI tensile strength. Class 10.9 is metric (marked "10.9") with similar strength (145,000+ PSI). They're roughly equivalent but have different thread specifications, so don't interchange them.

What size socket do I need for spark plugs?

Most modern spark plugs use 16mm (5/8") sockets, though some older or specialty plugs use 13/16" (21mm) or 18mm. Always verify your specific engine's spark plug size before purchase.

SAE to Metric Converter

Professional socket size charts, wrench conversions, bolt specifications, torque calculator, and more. Essential tool for mechanics and DIY enthusiasts.

25+ Socket SizesBolt SpecificationsTorque CalculatorTire Size Converter

Socket & Wrench Size Conversion Chart

Most Common Sizes

8mm

Battery terminals

10mm

Most common metric size - brackets

Essential!

12mm

Brake caliper bolts

13mm

Suspension bolts

14mm

Brake calipers

15mm

Specialty applications

17mm

Lug nuts

Essential!

19mm

Lug nuts

Essential!

21mm

Lug nuts (larger vehicles)

22mm

O2 sensors

SAE (Inches)	Decimal	Metric (mm)	Difference	Common Use
5/32"	0.1563	4mm	-0.03mm	Small electronics, precision work
3/16"	0.1875	5mm	+0.24mm	Small screws, trim pieces
7/32"	0.2188	5.5mm	+0.05mm	Hose clamps
1/4"	0.2500	6mm	-0.35mm	General fasteners, battery terminals
9/32"	0.2813	7mm	-0.14mm	Electrical components
5/16"	0.3125	8mm	+0.06mm	Common automotive fasteners
11/32"	0.3438	9mm	+0.27mm	Brake components
3/8"	0.3750	10mm	+0.48mm	Most common metric size!
7/16"	0.4375	11mm	-0.11mm	Transmission, engine bolts
1/2"	0.5000	13mm	+0.30mm	Suspension, drivetrain
9/16"	0.5625	14mm	-0.29mm	Brake calipers, wheel studs
19/32"	0.5938	15mm	-0.08mm	Specialty fasteners
5/8"	0.6250	16mm	+0.13mm	Engine accessories
11/16"	0.6875	17mm	-0.48mm	Lug nuts, drain plugs
3/4"	0.7500	19mm	-0.05mm	Lug nuts, axle nuts
13/16"	0.8125	21mm	+0.38mm	Lug nuts, spark plugs (some)
7/8"	0.8750	22mm	-0.23mm	Oxygen sensors, large bolts
15/16"	0.9375	24mm	+0.19mm	Axle nuts, suspension
1"	1.0000	25mm	-0.60mm	Large axle nuts
1-1/16"	1.0625	27mm	+0.02mm	Crank pulley, axle nuts
1-1/8"	1.1250	29mm	+0.43mm	Tie rod ends
1-1/4"	1.2500	32mm	+0.25mm	Axle nuts, hub nuts
1-5/16"	1.3125	33mm	-0.34mm	Large axle nuts
1-3/8"	1.3750	35mm	+0.08mm	Axle nuts
1-1/2"	1.5000	38mm	-0.10mm	Heavy equipment

Difference Guide: Green (<0.2mm) = Can usually interchange. Yellow (0.2-0.4mm) = Use correct size if possible. Red (>0.4mm) = Never interchange.

Socket Size Tips

10mm is king: The most commonly used (and lost!) metric socket size.

Close isn't good enough: Using the wrong size risks rounding bolt heads.

6-point vs 12-point: 6-point sockets grip better for high-torque applications.

Torque Tips

Calibrate your wrench: Check accuracy annually or after drops.

Clean threads: Dirty or lubricated threads affect torque readings.

Re-torque wheels: After 50-100 miles on new or rotated tires.

Bolt Grade Guide

Grade 5 (3 lines): 120,000 PSI - General automotive use.

Grade 8 (6 lines): 150,000 PSI - High-stress applications.

Class 10.9: Metric equivalent to Grade 8.

Frequently Asked Questions

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