Millimetres to Inches Converter for Canadian Workshops & Job Sites

Convert millimetres to inches instantly with our free online tool — built for Canadian DIYers and trades working between metric plans and imperial lumber, pipes, and sockets.

Canadian Metric & Imperial Length Converter

1 mm = 0.0393700787 in

The quick answer for 1 Millimeters — type any value below for the exact result

Enter Millimetres

Millimeters

Result in Inches

Inches

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 the width of a grain of rice. It is the default unit on technical drawings, machining tolerances, drill bits, bolts, and calipers in Canada and worldwide. Because it is small enough for precise work yet easy to scale up (1,000 mm = 1 m), it anchors most engineering measurement here — from Vancouver shipyards to Montreal aerospace shops.

Where it is used: Used across Canada in machining, engineering drawings, medicine (tumour sizes), photography (film and filters), and weather records — rainfall is measured in millimetres, snowfall in centimetres.

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 Canada's official standard following metrication in the 1970s.

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. Despite Canada's official metrication, inches remain everywhere in the trades: 2×4 lumber, drywall thickness, pipe threads, TV screen sizes, and personal height. 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 keeps metric-inch conversion a daily necessity in Canadian shops working with US suppliers.

Where it is used: Still standard in Canadian construction, plumbing, and carpentry, dominant in US manufacturing, and used internationally for display sizes and some aviation dimensions.

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, which Canada signed alongside the US and the UK.

Millimetres to Inches Conversion Table

Millimeters (mm)	Inches (in)
0.5 mm	0.0196850394 in
1 mm	0.0393700787 in
1.5 mm	0.0590551181 in
2 mm	0.0787401575 in
2.5 mm	0.0984251969 in
3 mm	0.1181102362 in
4 mm	0.157480315 in
5 mm	0.1968503937 in
6 mm	0.2362204724 in
8 mm	0.3149606299 in
10 mm	0.3937007874 in
12 mm	0.4724409449 in
15 mm	0.5905511811 in
20 mm	0.7874015748 in
25 mm	0.9842519685 in
50 mm	1.968503937 in
100 mm	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
A Canadian dime diameter (18.03 mm)	17.91 mm	0.7051181102 in

When You Need Millimeters to Inches Conversions

Tire Tread Depth Checks

Canadian tread gauges read millimetres, while charts and advice from the US use 32nds of an inch. Converting the 1.6 mm legal minimum to about 2/32 in — or the 4.8 mm (6/32 in) winter-tire guideline — tells you whether your tires are ready for another Prairie winter.

3D Printer Layer Heights

Slicer profiles mix a 0.4 mm nozzle with layer heights quoted in inches on North American forums. A 0.2 mm layer converts to 0.00787 in, which fits the "about 8 thou" advice you'll see in first-layer calibration threads.

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 — a letter-size F bit fits better, even if the big-box bins sort everything by fractions.

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 — a common pairing when Canadian shops work with US suppliers. 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 19 for the 19 mm lug nut found on most Canadian-market cars
2

See the Inch Result

The equivalent appears instantly: 19 mm = 0.74803 in, so you know a 3/4-inch socket (0.750 in) is close but the 19 mm socket 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 — exactly one inch, the thickness of a hockey puck

Why Use Be Converter?

Instant Precision Conversion

Get exact millimetre to inch results in real-time as you type — handy at the workbench, in the garage, or on the job site

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 — no guesswork between metric drawings and imperial tooling

Workshop Reference Table

Common metric sizes at a glance — from a 2 mm pilot bit to the 50 mm camera filter thread on your favourite lens

Swap with One Click

Toggle between mm and in instantly — essential when matching metric fasteners to imperial sockets, a daily reality in Canadian shops

Free & Unlimited

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

Completely Private

All calculations run locally in your browser. Your project measurements 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 snowblower shear-pin bolt 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 is a common socket size on import vehicles and flat-pack furniture, 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. Since Canadian hardware stores stock both systems side by side, converting between them is routine at the bits aisle.

What is 6 mm in inches for wrench 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). Canadian woodworkers use this shortcut constantly: think "25 mm per inch" and you are 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 for tire tread: most provinces set the legal minimum at 1.6 mm (about 2/32 in), and for winter driving experts recommend replacing tires below 4.8 mm (6/32 in) — a new tire starts near 8 mm (10/32 in).

Why do engineers prefer millimetres over inches?

Metric 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 micrometers (0.001 mm) and metres (1,000 mm), which keeps tolerances, sheet-metal gauges, and CAD units consistent — especially handy when Canadian shops collaborate with US suppliers.

About the Millimetres to Inches Converter

Our free online millimetres to inches converter gives instant, precise small-dimension conversions for the way Canadians actually build and make. Canada went metric in the 1970s, but imperial never left the job site: lumber is sold as 2×4s, pipe threads run by the inch, and socket sets come in both systems. Whether you're matching a metric bolt to an imperial socket in Ottawa, checking winter tire tread before a Winnipeg February, sizing drill bits from a Vancouver hardware aisle, or setting up a 3D printer in Montreal, this tool bridges metric drawings and imperial tooling at the precision that matters.

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.

Memorize 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 Japanese and European vehicles common on Canadian roads.

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.

Tire tread: new passenger tires start near 8 mm (0.315 in). The legal minimum across most provinces is 1.6 mm (2/32 in), but for Canadian winters replace winter tires below 4.8 mm (6/32 in) — snow traction fades fast below that. Quebec drivers, remember the mandatory winter-tire season runs December 1 to March 15.

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.