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Fastener Converter Metric

Inch

Metric

Converting between metric and inch fasteners forces you to make compromises. This converter gives you best proposals and will show you the differences in an easy way.

The highlighted result is the closest match.

Metric

UNC

UNF

#0-80

BSW

BSF

Inch/Imperial

Metric Coarse

M1.6 x 0.35p

Metric Fine

Metric Extra Fine

You can also view and print our handy Thread Pitch Chart

View Thread Pitch Chart

Need help identifying what size is my Bolt / Screw? Measure the outside of the thread and select from the dropdown below to see the closest match.

For accuracy we recommend using a vernier. Measurements are intended to be used as a guide only.

Outside diameter of the thread

Metric Coarse

M1.6 x 0.35p

Metric Fine

Metric Extra Fine

UNC

UNF

#0-80

BSW

BSF

BA

Screw Gauge

Select a size to view outside diameter measurements You know the size screw but want to cross check the diameter. Select the size from the dropdown to see the closest match.

Screw Type	Thread Type	Outside Diameter of Thread

Calculators Decimal

Fractions

Inches

Millimetres

The calculators below will translate Imperial measurements to Metric, or Metric to Imperial. Imperial is also known as English or Standard measurement.

Convert Fraction to

Millimeters

0.00 mm

Convert Millimeters to

Fraction

0/0 "

Convert Decimal to

Millimeters

0.00 mm

Convert Millimeters to

Inches

0.0000 "

You can also view and print our handy Metric to Imperial Chart

View Metric to Imperial Chart

Converting Metric to Imperial, or Imperial to Metric, may be helpful in some cases, but it will not work with machine screws, cap screws, nuts, or other parts that require matching thread counts. There is no equivalency on thread counts.

Converting Standard Fractions to Decimals is just a matter of division, but for a quick easy calculation, you can use the calculator below.

Convert Fraction to

Decimal (Imperial)

0.00 "

Thread Pitch Converter mm (pitch)

tpi (threads per inch)

mm (pitch)

Will help if you need to convert an imperial TPI (threads per inch) thread to Metric Pitch thread or a Metric Pitch thread to an imperial TPI (threads per Inch) thread. Useful when a size is no longer available and you want the same thread style (e.g. a coarse or fine thread).

Convert TPI
(threads per inch)
to

Pitch (mm)

0.00

Will return the closest match, for exact refer to our thread pitch chart

Convert Pitch (mm) to

TPI (threads per inch)

0.0

Will return the closest match, for exact refer to our thread pitch chart

You can also view and print our handy Thread Pitch Chart

View Thread Pitch Chart

Spanner Sizes Metric and Imperial

Metric Thread Size

Class 4.6/8.8/10.9
Low & High Tensile

3.2mm

Class 8.8/10.9
DIN + JIS

A2/A4
Stainless DIN

AS1252
Structural

Imperial Thread Size

Grade 2
BSW Low
Tensile

5/16"

Grade 5/8
IFI

Grade 2/5/8
UNC & UNF
Low & High Tensile

Grade R
BSF High
Tensile

A2/A4
Stainless

5/16"

Allen Key Sizes Metric and Imperial

Select a Socket Screw Size to see Matching Key Size Metric

Metric Thread Size

Socket Head
Cap

1.5mm

Low Head Cap
Socket

Button Head
Socket

Countersunk
Socket

Set Screw (Grub)
Socket

0.7mm

Shoulder Screw
Socket

Imperial

Imperial Thread Size

Socket Head
Cap

0.050"

Low Head Cap
Socket

Button Head
Socket

0.035"

Countersunk
Socket

0.035"

Set Screw (Grub)
Socket

0.028"

Shoulder Screw
Socket

Select a Allen Key Size to see Matching Socket Screw Size Metric

Metric Allen Key Size

Socket Head
Cap

Low Head Cap
Socket

Button Head
Socket

Countersunk
Socket

Set Screw (Grub)
Socket

M1.6

Shoulder Screw
Socket

Imperial

Imperial Allen Key Size

Socket Head
Cap

Low Head Cap
Socket

Button Head
Socket

Countersunk
Socket

Set Screw (Grub)
Socket

#0 & #1

Technical Resources

Metric

UNC

UNF

BSW

BSF

Inch/Imperial

Metric Coarse

Metric Fine

Metric Extra Fine

Outside diameter of the thread

Metric Coarse

Metric Fine

Metric Extra Fine

UNC

UNF

BSW

BSF

BA

Screw Gauge

You can multiselect to compare sizing

Convert Fraction to

Millimeters

Convert Millimeters to

Fraction

Convert Decimal to

Millimeters

Convert Millimeters to

Inches

Convert Fraction to

Decimal (Imperial)

Convert TPI (threads per inch) to

Pitch (mm)

Convert Pitch (mm) to

TPI (threads per inch)

Metric Thread Size

Class 4.6/8.8/10.9 Low & High Tensile

Class 8.8/10.9 DIN + JIS

A2/A4 Stainless DIN

AS1252 Structural

Imperial Thread Size

Grade 2 BSW Low Tensile

Grade 5/8 IFI

Grade 2/5/8 UNC & UNF Low & High Tensile

Grade R BSF High Tensile

A2/A4 Stainless

Metric Thread Size

Socket Head Cap

Low Head Cap Socket

Button Head Socket

Countersunk Socket

Set Screw (Grub) Socket

Shoulder Screw Socket

Imperial Thread Size

Socket Head Cap

Low Head Cap Socket

Button Head Socket

Countersunk Socket

Set Screw (Grub) Socket

Shoulder Screw Socket

Metric Allen Key Size

Socket Head Cap

Low Head Cap Socket

Button Head Socket

Countersunk Socket

Set Screw (Grub) Socket

Shoulder Screw Socket

Imperial Allen Key Size

Socket Head Cap

Low Head Cap Socket

Button Head Socket

Countersunk Socket

Set Screw (Grub) Socket

Shoulder Screw Socket

Convert TPI
(threads per inch)
to

Class 4.6/8.8/10.9
Low & High Tensile

Class 8.8/10.9
DIN + JIS

A2/A4
Stainless DIN

AS1252
Structural

Grade 2
BSW Low
Tensile

Grade 5/8
IFI

Grade 2/5/8
UNC & UNF
Low & High Tensile

Grade R
BSF High
Tensile

A2/A4
Stainless

Socket Head
Cap

Low Head Cap
Socket

Button Head
Socket

Countersunk
Socket

Set Screw (Grub)
Socket

Shoulder Screw
Socket

Socket Head
Cap

Low Head Cap
Socket

Button Head
Socket

Countersunk
Socket

Set Screw (Grub)
Socket

Shoulder Screw
Socket

Socket Head
Cap

Low Head Cap
Socket

Button Head
Socket

Countersunk
Socket

Set Screw (Grub)
Socket

Shoulder Screw
Socket

Socket Head
Cap

Low Head Cap
Socket

Button Head
Socket

Countersunk
Socket

Set Screw (Grub)
Socket

Shoulder Screw
Socket