Millimetres to Inches Converter for Aussie Sheds & Workshops

Convert mm to in as you type.

Metric Length Converter - cm, m, km & Miles

1 mm ≈ 0.0393700787 in

Reference for one unit; displayed values may be rounded.

Enter Millimetres

Millimeters

Use a dot or comma for decimals, without thousands separators.

Result in Inches

Inches

Decimal places

Display rounding does not improve the accuracy of your original measurement. Very large or very small results use scientific notation.

Method and source

mm to in Conversion Formula

To convert millimetres to inches, divide the millimetre value by 25.4. This works because one inch is defined as exactly 25.4 millimetres, so 1 mm = 0.03937 in.

1 mm ≈ 0.0393700787 in

Millimeters and Inches Explained

Millimeters (mm)

The millimetre is a metric unit of length equal to one thousandth of a metre — about 0.039 inches, roughly the thickness of a credit card (0.76 mm) or a grain of rice width. It is the default unit on technical drawings, machining tolerances, drill bits, bolts, and calipers across Australia and most of the world. Because it is small enough for precise work yet easy to scale up (1,000 mm = 1 m), it anchors most engineering measurement in metric countries — including ours since the 1970s.

Where it is used: Used worldwide in machining, construction fasteners, medicine (tumour sizes), photography (film and filters), and rainfall records — the Bureau of Meteorology measures every storm in millimetres.

Origin: Created with the metric system in 1795 from the Latin 'mille' for thousand; it became the workhorse unit of industrial measurement during the 19th century and replaced inches across Australia through the 1970s metric conversion.

Inches (in)

The inch is a US customary and imperial unit of length equal to exactly 25.4 millimetres, or one twelfth of a foot. It is the standard unit for screen diagonals, pipe threads, lumber, and wrench sizes in the United States — and it still lingers in Australia on TV sizes, bike wheels, and the plumbing in older homes. In machine-shop practice it is often divided into 1/64-inch increments or expressed as thousandths ('thou'), so 0.5 in reads as 500 thou — a habit that makes metric-inch conversion a daily necessity in mixed workshops.

Where it is used: Dominant in US manufacturing, plumbing, and carpentry; officially retired in Australia but still used for TV and monitor sizes, bike wheel diameters, and hardware imported from the States.

Origin: Derived from the Roman 'uncia' (one twelfth), traditionally the width of a thumb; fixed at exactly 2.54 cm by the 1959 international yard and pound agreement — the same standard Australia adopted during its 1970s metric conversion.

Millimetres to Inches Conversion Table

Select a value to use it in the calculator.

Millimeters (mm)	Inches (in)
	0.0196850394 in
	0.0393700787 in
	0.0590551181 in
	0.0787401575 in
	0.0984251969 in
	0.1181102362 in
	0.157480315 in
	0.1968503937 in
	0.2362204724 in
	0.3149606299 in
	0.3937007874 in
	0.4724409449 in
	0.5905511811 in
	0.7874015748 in
	0.9842519685 in
	1.968503937 in
	3.937007874 in

Inches to Millimeters Conversion Table

Inches (in)	Millimeters (mm)
0.0625 in	1.5875 mm
0.125 in	3.175 mm
0.25 in	6.35 mm
0.5 in	12.7 mm
0.75 in	19.05 mm
1 in	25.4 mm
2 in	50.8 mm
4 in	101.6 mm
8 in	203.2 mm
12 in	304.8 mm
16 in	406.4 mm

Millimeters to Inches in Everyday Objects

Common real-world examples that make Millimeters and Inches easy to picture at a glance.

	Millimeters (mm)	Inches (in)
A credit card thickness	0.76 mm	0.0299212598 in
A pencil lead diameter	0.7 mm	0.0275590551 in
A CD disc thickness	1.2 mm	0.0472440945 in
A grain of rice	6 mm	0.2362204724 in
An M8 bolt diameter	8 mm	0.3149606299 in
An Australian 5 cent coin diameter	17.91 mm	0.7051181102 in

When You Need Millimeters to Inches Conversions

Tyre Tread Depth Checks

Tread depth gauges in Australia read millimetres, but plenty of imported gauges and online charts use 32nds of an inch. Converting the 1.5 mm legal minimum to about 2/32 in — and the recommended 3 mm replacement point to 0.118 in — tells you whether the tyres see out another wet season.

3D Printer Layer Heights

Slicer profiles mix a 0.4 mm nozzle with layer heights quoted in inches on overseas forums and YouTube. A 0.2 mm layer converts to 0.00787 in, which fits the 'about 8 thou' advice those threads give for first-layer calibration.

Matching Drill Bits to Bolts

A metric clearance hole for an M6 bolt is 6.5 mm. The imperial bit box starts at 1/4 in, so converting 6.5 mm to 0.2559 in confirms the 1/4 bit (6.35 mm) is a touch tight — better to step up a metric size than risk splitting a sheet of ply.

Machining Tolerances on Mixed Drawings

A shaft journal specified at 19.05 mm ±0.05 mm must mate with a bearing bore drawn in inches for an imported machine. Converting 19.05 mm to exactly 0.75 in keeps the press fit inside the 0.002 in tolerance band the customer expects.

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How to Use

1

Enter the Millimetre Value

Type the dimension in millimetres — for example, enter 12 for an N12 bar in a concreting job, or 16 for the wheel nuts on an imported car
2

See the Inch Result

The equivalent appears instantly: 16 mm = 0.62992 in — a whisker over the 5/8-inch sockets (0.625 in) in the old imperial set, which is why only the 16 mm fits properly
3

Copy or Swap

Copy the result to your clipboard or click Swap to convert inches back to millimetres
4

Use the Conversion Table

Check the table for common values like 6 mm = 0.23622 in or 25 mm = 0.98425 in

Why Use Be Converter?

Instant Precision Conversion

Get exact millimetre to inch results in real-time as you type — no calculators at the workbench and no doing the maths in your head

Machining-Grade Accuracy

Uses the exact standard of 25.4 mm per inch, so an M8 bolt shank converts to 0.31496 in with full precision

Workshop Reference Table

Common metric sizes at a glance — from a 2 mm pilot-hole drill bit to a 50 mm camera filter thread

Swap with One Click

Toggle between mm and in instantly — dead handy when new metric hardware has to mate with Grandad's old imperial tools

Free & Unlimited

No signup, no limits, no worries. Convert as many dimensions as your project needs — always free

Completely Private

All calculations run locally in your browser. Your project plans and drawings never leave your device

Frequently Asked Questions

How many inches are in 1 millimetre?

1 millimetre equals 0.03937 inches. This comes directly from the definition of 1 inch as exactly 25.4 mm — one millimetre is therefore 1/25.4 of an inch.

How do I convert mm to inches manually?

Divide the millimetre value by 25.4. For example, a 12 mm spanner target is 12 ÷ 25.4 = 0.47244 in. A quick estimate: divide mm by 25 — 12 ÷ 25 = 0.48 in, within 2% of the exact answer.

What is 10 mm in inches?

10 millimetres equals 0.3937 inches — just under 4/10 of an inch. It's the classic size for battery terminals on the ute, sensor stacks, and standoffs, and it sits between the 3/8 in (9.525 mm) and 7/16 in (11.1125 mm) imperial marks.

How many mm is a 1/4 inch drill bit?

A 1/4 inch bit is 6.35 mm exactly. Other common equivalences: 1/8 in = 3.175 mm, 1/2 in = 12.7 mm, and 3/4 in = 19.05 mm. Metric bit sets on the shelf skip these values, so conversion is routine when working from American plans or imports.

What is 6 mm in inches for spanner sizes?

6 mm equals 0.23622 in, which is just under 1/4 inch (0.25 in). In practice a 6 mm fastener needs a 6 mm socket — the nearest imperial size, 1/4 in, is loose enough to round off the hex corners.

What is 100 mm in inches?

100 millimetres equals 3.937 in — almost exactly 4 inches (101.6 mm). Cabinetmakers and chippies use this shortcut constantly: think '25 mm per inch' and you're within 1.6% of the exact 25.4 factor.

Is 5 mm bigger than 1/4 inch?

No. 5 mm converts to 0.19685 in, which is smaller than 0.25 in (6.35 mm). The crossing point matters with tyre tread depth: the Australian legal minimum of 1.5 mm is about 2/32 in, while a new tyre starts near 8 mm (10/32 in).

Why do engineers prefer millimetres over inches?

Australia went fully metric back in the 1970s for good reason: drawings in millimetres avoid fractional and decimal-inch mixing — 1/64 in increments force awkward numbers like 0.396875 mm. Millimetres also scale cleanly with micrometres (0.001 mm) and metres (1,000 mm), keeping tolerances, sheet-metal gauges, and CAD units consistent.

About Millimetres to Inches Converter

Our free online millimetres to inches converter gives instant, precise small-dimension conversions for the shed, the workshop, and the home reno. Australia has been metric since the 1970s, yet inches still crop up everywhere — TV and monitor sizes, bike wheels, plumbing in older homes, hardware shipped from the US, and half the DIY videos online. Whether you're matching a metric bolt to an imperial socket, sizing drill bits from an American plan, checking tyre tread against an old chart, or setting up a 3D printer, this tool bridges the two systems at the precision where it matters most.

Expert Tips for mm to in Conversion

The exact factor is 1 mm = 0.0393701 in, because 1 inch is defined as exactly 25.4 mm. Dividing by 25.4 always gives the exact answer — never round before the final step.

Memorise socket landmarks: 8 mm = 0.31496 in, 10 mm = 0.3937 in, 13 mm = 0.51181 in (close to 1/2 in), and 17 mm = 0.66929 in. These cover most fasteners on the ute, the trailer, and the mower.

For 3D printing, a standard 0.4 mm nozzle extrudes layers from 0.1 to 0.32 mm — that is 0.00394 to 0.0126 in. Slicers mix units, so keep the 25.4 factor handy.

Tyre tread: new tyres start near 8 mm (0.315 in), most tyre fitters recommend replacing by 3 mm (0.118 in) for safe wet-weather braking, and the Australian legal minimum is 1.5 mm (about 2/32 in). Charts marked in 32nds convert at 4/32 in ≈ 3.2 mm.

Printed circuit board work jumps between units constantly: a 1.6 mm standard board is 0.06299 in, and 2.54 mm pin pitch equals exactly 0.1 in — the classic DIP spacing in any electronics parts catalogue.

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