Dyne to pound-force: the pull of a mosquito
What this conversion does
Insect flight, surface films and single filaments produce forces between a few dynes and a few thousand, and those measurements are nearly always recorded in dynes. The identical force written in pound-force needs six or seven zeroes in front of its first significant digit, so the two columns of a conversion table look nothing alike in length even though every row describes one quantity. The factor is 0.000002248, fixed by the definitions of the pound and the metre.
What a handful of dynes looks like
A mosquito of two milligrams presses down with a force of about two dynes. A water strider spreads its weight over six long legs, and the surface film under each one pushes back with a few dynes of its own. A human hair, strong for its diameter, holds roughly a hundred thousand dynes before it snaps — a load that a pound-force scale would express as a fraction of a pound.
Dyne to pound-force conversion table
Forces at the small end of the scale, with the pound-force column written out in full so the order of magnitude is unmistakable instead of hidden behind an exponent.
| Dyne (dyn) | Pound-force (lbf) |
|---|---|
| 1 | 0.000002248089431 |
| 100 | 0.0002248089431 |
| 1000 | 0.002248089431 |
| 10000 | 0.02248089431 |
| 100000 | 0.2248089431 |
| 1000000 | 2.248089431 |
Why the pound-force gets unwieldy down here
The pound-force is sized for the things people weigh — a bag of flour, a suitcase, a person — so its useful range sits far above the tug of an insect. Below a few hundred dynes the pound-force value is mostly leading zeroes, and comparing two such figures by eye stops being possible. The dyne keeps the same measurements in whole numbers that can be read at a glance.
A milligram-force is a dyne, near enough
One milligram-force, the weight of a small grain of sand, is 0.980665 dynes. Rounded, a dyne is the force one milligram exerts under gravity, which gives a fast sanity check: a reading of forty dynes is about the weight of forty milligrams of matter.
Frequently asked questions
How small a force can this converter handle?
Any positive value, and the arithmetic is exact for all of them. The practical limit is display rather than precision: below about a thousandth of a dyne the answer is written in exponent form, because a full decimal expansion would be almost entirely zeroes and the significant digits would be easy to lose.
What does a mosquito weigh in pound-force?
A two-milligram mosquito presses down with roughly two dynes, which is about 0.0000045 lbf. The pound-force figure is only legible once an exponent is allowed, and that is the practical argument for quoting tiny forces in dynes instead.
Why is the pound-force value always so close to zero?
Because a pound-force is a large unit and these are small quantities. One pound-force is 444822 dynes, so a force of single or double digits of dynes lands in the sixth decimal place of a pound-force. The digits are right; there are simply a great many zeroes ahead of them.
Can a surface tension reading be converted the same way?
Only after multiplying by the length involved. Surface tension is a force per unit length, quoted in dynes per centimetre, so a reading must be multiplied by the contact length before it becomes a force that can be expressed in pound-force at all.
Which unit should go in an engineering report?
Whichever one the reader can act on. A specification written around imperial hardware usually states small loads in pound-force, sometimes with an ounce-force or gram-force figure beside it, while a physics measurement of the same quantity is almost always more readable in dynes.