Engineering unit converter

Why show every unit at once

Most converters make you choose a target unit before they will tell you anything. That is the wrong interaction for engineering work, where the useful operation is usually “show me this quantity in every unit somebody on this project might use.” A vendor quotes psi, the client specifies bar, the analysis runs in pascals, and the drawing says kPa. You want all four.

On precision

Conversions here carry six significant figures and use exact definitions where they exist — the inch is exactly 25.4 mm, the pound-force is exactly 4.4482216152605 N. The tool rounds for display, not internally.

The ones that bite

• Gauge and absolute pressure. No conversion factor will save you. 100 kPa gauge and 100 kPa absolute differ by an atmosphere.
• Pound-mass and pound-force. Related by g, not equal. This converter keeps them in separate families on purpose.
• Tons. Short, long, metric — and a ton of refrigeration, which is a rate of heat flow and not a mass at all.
• Gallons. A US gallon is 3.785 L. An imperial gallon is 4.546 L. Twenty per cent apart, same word.