Unit Conversion
Switching safely between SI, metric and imperial units without losing the plot.
Why this matters
Where it occurs
Drawings in inches meet materials in millimetres; gauges in psi meet pump curves in metres. Conversions are daily bread.
Why calculate it
Every formula expects consistent units - mixed units are the single biggest source of calculation error in the trades.
What decision it supports
Which unit does this formula need? Is this answer plausible in the target unit?
What happens if it is wrong
A missed conversion can shift a result by 25.4x, 60x or 1000x - misalignment tolerance errors are exactly how expensive mistakes happen.
The concept
Conversion is multiplication by a known factor: 1 inch = 25.4 mm, 1 psi = 6.895 kPa, 1 hp = 0.7457 kW.
Temperature is the exception: it converts with an offset, °C = (°F - 32) x 5/9.
The professional habit is the sanity check: convert first, calculate second, and ask whether the answer makes sense in the target unit.
Formula
Conversion Factor
value_new = value_old x factor
- factor = Known conversion factor (-)
Worked example
Problem: Convert 3.5 inches to millimetres.
- Use 1 in = 25.4 mm.
- Multiply: 3.5 x 25.4.
- Calculate: 88.9 mm.
88.9 mm - the dimension to machine or measure against.
Quick solve: practice it
Convert 10 horsepower to kilowatts. (1 hp = 0.7457 kW)
Quick-solve habit: calculate, then ask yourself - does this answer make sense in real units?
Games that use this mathematics
Apply the calculation inside a workplace simulation.