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Unit Converter for Metal Workshops
See length and mass units side by side on one screen: mm, inch, cm and m equivalents for drawings and quotes, plus kg and metric tonnes.
Length
1 inch = 25.4 mm (ISO). Choose the input unit and enter a value; the other units update automatically.
- mm
- 100
- in
- 3.937008
- cm
- 10
- m
- 0.1
Mass
Metric tonne: 1 t = 1,000 kg. Not to be confused with the US short ton or the imperial long ton.
- kg
- 1
- tonne (t)
- 0.001
Why use a unit converter in the workshop?
Technical drawings often arrive in inches while ERP systems and quotes work in millimetres or metres. This converter uses the international inch definition, 1 inch = 25.4 mm exactly, and derives cm and m from it: 1 cm = 10 mm, 1 m = 1,000 mm. For example, a 0.25 inch sheet is 6.35 mm thick, and 100 mm equals about 3.937 inches.
For mass, the tool uses the metric tonne: 1 t = 1,000 kg. It is not the same as the US short ton (about 907 kg) or the imperial long ton (about 1,016 kg), which still appear in some older documents and freight quotes.
Aligning units before calculating sheet thickness, profile cross-sections or package weights reduces the risk of errors in quotes and production orders.
How to use the results
The results are technical estimates. For a binding quote, material price, scrap, labour and your own shop rules also have to be taken into account.
Frequently asked questions
How many millimetres are in an inch?
Exactly 25.4 mm, according to the international (ISO) definition. All mm, cm and m values in the converter are derived from this constant.
How do I convert mm to inches?
Divide the millimetre value by 25.4. For example, 100 mm ÷ 25.4 ≈ 3.937 inches and 3 mm ≈ 0.118 inches.
How do I convert inches to millimetres?
Multiply the inch value by 25.4. For example, 1/4 inch = 0.25 × 25.4 = 6.35 mm and 1/8 inch = 3.175 mm.
Is a tonne the same as 1,000 kg?
Yes. A metric tonne (t) is 1,000 kg. The US short ton (about 907 kg) and the imperial long ton (about 1,016 kg) are different units and are not used here.
Can I use the results directly in quotes?
The conversion is mathematically exact. If the customer's specification requires special rounding or tolerances, apply them separately.
Related calculators
- Scrap rate calculatorLinear scrap in mm and as a percentage from bar stock length and the total length cut from it.
- Cutting length estimatorRough cutting length in mm and m from a rectangle or circle outline plus free segments — no DXF needed.
- Sheet metal weight calculatorApproximate sheet weight in kg from length, width, thickness and material density.
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