What is microgram?
A microgram is a metric unit of mass equal to one millionth of a gram. It is used in analytical chemistry, toxicology, pharmacology, and measuring trace amounts of substances in laboratory settings.
Real-world uses
Micrograms are used for precise pharmaceutical dosages (e.g., 25 µg levothyroxine), trace element measurements in blood tests, and contaminant detection in water and food safety testing. Vitamin D and B12 are commonly dosed in micrograms.
History
The microgram became important with the development of analytical chemistry and pharmacology in the 20th century. The prefix "micro-" comes from the Greek "mikros" meaning small. It was formalized as an SI prefix in 1960.
Common mistakes
Misreading "µg" as "mg," leading to a 1000-fold dosing error—a potentially lethal mistake in medicine. Some prescribing guidelines mandate writing "microgram" in full to prevent this confusion.
What is stone?
A stone is a unit of mass used primarily in the United Kingdom and Ireland, equal to 14 pounds. It is mainly used to express human body weight in everyday conversation.
Real-world uses
The stone is used primarily in the UK and Ireland for expressing body weight (e.g., "I weigh 11 stone"). It appears on bathroom scales sold in Britain and is the preferred unit in British medical consultations for patient weight discussions.
History
The stone has been used in the British Isles since at least the 14th century for weighing agricultural goods. Its value varied historically (from 4 to 32 pounds depending on the commodity) before being fixed at 14 pounds by the Weights and Measures Act of 1835.
Common mistakes
Assuming a stone is used outside the British Isles—it is virtually unknown in the US, continental Europe, or most other countries. Also, forgetting that 1 stone = 14 pounds, not 10 or 12.
When is this conversion used?
Converting between microgram and stone is common when working across metric and imperial systems, such as international trade, travel between countries with different measurement standards, or following instructions from a different region.
Worked examples
1 microgram = 1.574730e-10 stone
1 stone = 6.35029318 kilogram
How to convert microgram to stone
To convert microgram to stone, multiply the value by 1.574730e-10.
To convert stone back to microgram, multiply by 6.350293e+09.
Measurement standards
The kilogram is defined by fixing the Planck constant to exactly 6.62607015 × 10⁻³⁴ joule-seconds, as established at the 26th General Conference on Weights and Measures in 2018. This ended the last SI definition based on a physical artefact.
Did you know?
The International Prototype of the Kilogram, a platinum-iridium cylinder stored near Paris since 1889, was found to have drifted by about 50 micrograms relative to its copies over a century — roughly the mass of a fingerprint.
Quick reference: microgram to stone
| microgram | stone |
|---|---|
| 0.1 | 1.574730e-11 |
| 0.5 | 7.873652e-11 |
| 1 | 1.574730e-10 |
| 2 | 3.149461e-10 |
| 5 | 7.873652e-10 |
| 10 | 1.574730e-09 |
| 25 | 3.936826e-09 |
| 50 | 7.873652e-09 |
| 100 | 1.574730e-08 |
| 250 | 3.936826e-08 |
| 500 | 7.873652e-08 |
| 1,000 | 1.574730e-07 |
Common values
| microgram | stone | |
|---|---|---|
| A paperclip | 999,999,999.99999988 microgram | 0.15747304 stone |
| A smartphone | 1.750000e+11 microgram | 27.55778277 stone |
| A bag of sugar | 999,999,999.99999988 microgram | 0.15747304 stone |
| Average adult human | 7.000000e+10 microgram | 11.02311311 stone |
| A small car | 1.200000e+12 microgram | 188.9676533 stone |