The U-100, 0.5 mL barrel

100 units to the millilitre, 50 units of capacity, marked every 1 unit. Everything below is computed from those three figures.

Educational arithmetic only. Not medical advice and not a dosing protocol.

The three numbers every other figure on this page comes from. All three are printed on the barrel itself, so none of them is a claim this page is making.
Property	Value
Units to the millilitre	100
Capacity	0.5 mL, which is 50 units
Smallest printed mark	1 unit, which is 10.0 microlitres
Half a mark	5.0 microlitres

What the bench will not tell you

This is educational arithmetic on figures entered by the reader. It is not medical advice, not a dosing protocol, and not a recommendation that anything be prepared, obtained or administered.

Nothing here states what quantity is appropriate for anyone, and there is no function in it that produces an amount to administer. A question about anyone’s health belongs with a licensed clinician who can examine the person asking.

Compounds of the kind this arithmetic is used on are largely research chemicals that are not approved by the FDA for human use. An exact calculation is not an accurate measurement: what is actually in a syringe depends on the preparation and the device, neither of which this page can see.

No qualified clinical reviewer is recorded against this site, and no credential is claimed anywhere on it. the limits of this bench.

What is particular to this barrel

The same calibration as the 1 mL barrel and half the capacity, which makes it the quiet failure of the five. The arithmetic is identical, so a reading computed for a U-100 is correct here, right up until it comes out above fifty and describes a draw that will not fit. Nothing about the number looks wrong. The barrel is simply shorter than the answer.

Fifty units over half a millilitre is the same spacing as the 1 mL barrel, so the marks are no finer - there are just fewer of them. The accuracy is identical; only the ceiling moves.

Every row is computed from this barrel's own calibration of 100 units to the millilitre. The last column is half a graduation as a share of that draw, which is the smallest reading error the barrel can have at that point on its scale.
Reading, units	Volume, mL	Volume, microlitres	Half a mark, as % of the draw
2.5	0.025	25	20.00%
5.0	0.050	50	10.00%
10.0	0.100	100	5.00%
15.0	0.150	150	3.33%
20.0	0.200	200	2.50%
25.0	0.250	250	2.00%
35.0	0.350	350	1.43%
40.0	0.400	400	1.25%
45.0	0.450	450	1.11%
50.0	0.500	500	1.00%

Where the reading error stops being ignorable

Half a graduation on this barrel is 5.0 microlitres, and that figure does not change with the size of the draw. As a share of the draw it therefore grows as the draw shrinks: at 2 units it is 25.0%, and it keeps climbing from there.

Below two graduations every tool on this bench flags the reading rather than printing it plainly, because at that point the uncertainty in the measurement is a large fraction of what is being measured and the precision of the arithmetic has stopped meaning anything. The fix is not a better calculation. It is more liquid, which is what thinning a solution is for.

The same printed number read on all five barrels. U-100, 0.5 mL is one column of this table, and the spread across the row is the reason no tool here defaults the barrel for you.
Printed reading	U-100, 1 mL	U-100, 0.5 mL	U-100, 0.3 mL	U-50, 0.5 mL	U-40, 1 mL
5 units	0.050 mL	0.050 mL	0.050 mL	0.100 mL	0.125 mL
10 units	0.100 mL	0.100 mL	0.100 mL	0.200 mL	0.250 mL
20 units	0.200 mL	0.200 mL	0.200 mL	0.400 mL	0.500 mL
30 units	0.300 mL	0.300 mL	0.300 mL	past the barrel	0.750 mL
40 units	0.400 mL	0.400 mL	past the barrel	past the barrel	1.000 mL
50 units	0.500 mL	0.500 mL	past the barrel	past the barrel	past the barrel

What this page is not saying

Everything here is a property of a manufactured object: how it is marked, how much it holds, and what follows arithmetically from those two facts. Nothing on this page says which barrel anybody should use, what should go in it, or what any reading on it should be. A calibration is a measuring scale, and a measuring scale has no opinion about what is measured with it.

Next to this on the bench

The barrel reading tool
This barrel, any volume, either direction.
The other four barrels
Same treatment, different three numbers.
Rounding to the nearest mark
The reading-error arithmetic in full.