Engineering & Physics

Free engineering and unit tools

Every conversion here works in every direction, not just one way, and runs instantly in your browser. These engineering tools are free with no sign-up — quick answers for units, electricity and material densities whenever you need them.

Three tools, a wide reach

Unit converter handles length, weight, volume, area, temperature, energy and data size, and every category works in every direction rather than one way only. It keeps the distinctions that catch people out: a nautical mile is not a statute mile, a US gallon is not an imperial gallon, and a US ton is not a UK ton. They are separate units here instead of one averaged guess. Data size keeps binary and decimal apart too, so a KiB of 1024 bytes never gets confused with a KB of 1000. Temperature is the one category that is not a simple multiplication, since each scale has its own zero point; the converter handles that properly and warns you when a value falls below absolute zero. Electrical calculator covers Ohm’s law and power: fill in any two of volts, amps, ohms and watts and it works out the other two, in all six combinations, plus energy over time in joules, watt-hours or kilowatt-hours. Density comparator answers the “which is heavier” question properly — by volume and by material, across about thirty-five metals, gemstones, woods, liquids and gases — and converts gemstone carats to volume.

Common questions

Why can’t I convert volts to joules?

Because they measure different things, and no conversion factor between them exists. A volt is electrical pressure; a joule is a quantity of energy. To get from one to the other you need a second quantity — current and time, or charge. The Electrical calculator does exactly that, and the page explains it rather than quietly producing a meaningless number.

Are the density figures reliable?

They are standard physical constants — the published density of steel, gold, oak or water — rather than values copied from another site’s table. Natural materials such as wood vary from sample to sample, so treat those as typical rather than exact. Metals and pure liquids are consistent.

Why keep US and imperial gallons separate?

Because they differ by about twenty per cent — 3.785 litres against 4.546 — and a recipe, a fuel figure or a tank capacity converted with the wrong one is simply wrong. The same goes for tons and for fluid ounces. A site that offers a single unlabelled “gallon” is making that choice for you without saying which one it picked.

Do these work offline?

Once the page has loaded, yes. The arithmetic happens in your browser with no further requests, so losing your connection mid-calculation changes nothing. Nothing you type is sent anywhere or recorded.

Is a kilocalorie the same as a calorie?

Not literally, and food labels are where this catches people out. The “calories” printed on a label are kilocalories — a thousand of the physics calorie. The Unit converter keeps both, so kcal to kJ gives you the number a nutrition label means, while cal to J gives the physics one. The calorie here is the thermochemical calorie, exactly 4.184 joules.