Mass converter
Mass converter, no network, no rounding surprises.
Runs on your device. The file is never uploaded.
Mass converter scales a value across mg, g, kg and t plus lb, oz and st. The pound sits at 0.45359237 kg and a stone is fourteen of those, 6.35029318 kg. t here is the metric tonne of 1000 kg; the US short ton and UK long ton are absent from the table.
Questions
Which mass units are supported?
Seven: kg, g, mg, t, lb, oz and st. Kilograms are the base. A pound is 0.45359237 kg by definition, an ounce is 0.028349523125 kg, and a stone is 6.35029318 kg, which is fourteen pounds. Both the from and to units must be chosen, since neither carries a default.
Is t a metric tonne or a ton?
A metric tonne, exactly 1000 kg. The US short ton of 2000 lb and the UK long ton of 2240 lb are not in the table, so do not read t as either of them. If you need a short ton, convert your value to lb and divide by 2000 yourself.
Which ounce is oz?
The avoirdupois ounce, 0.028349523125 kg, one sixteenth of a pound. It is a mass, not a volume: a fluid ounce is a different unit and lives in the volume converter. The troy ounce used for precious metals is not in this table either, and it is heavier than the avoirdupois one.
Can it convert weight into mass?
No, and the distinction matters less here than it sounds. Every unit in the table is a mass, and each conversion is a ratio between masses, so the answer holds anywhere. Newtons, pounds-force and anything else involving gravity are outside what this tool does.
Why did my value not parse?
The field is read as a plain number, so anything else stops with "value must be a number". Strip the unit out of the value, use a dot for the decimal point and remove thousands separators. Scientific notation such as 2.5e3 is accepted. The dropdowns carry the units, so the value box should hold digits only.
Does anything leave my browser?
No. It is one multiplication and one division against a table compiled into the page, run in a Web Worker. There is no request, no account and no saved history, and the page still converts with the network switched off after the first visit.