# What is the accuracy of medical syringes?

I am interested in both low and high volume syringes.

• Note that the accuracy is also limited by your ability to manipulate and read the plunger. (Digresseion:I once spent half a day moving single grains of a cmpound on and off a balance, trying to get another digit of precision, when I should instead have taken the mass I had and adjusted the amount of solvent... which would still have been overprecise for the intended use.) – keshlam Nov 22 '15 at 19:54

The requirements for ordinary sterile single-use syringes made of plastic materials are standardized in the international standard ISO 7886-1:1993 Sterile hypodermic syringes for single use – Part 1: Syringes for manual use.

According to this standard, the tolerance on the graduated capacity depends on the nominal capacity of the syringe $V$ and the expelled volume $V_\text{ex}$.

For syringes with a nominal capacity of $V\lt5\ \mathrm{ml}$, the tolerance amounts to

• $\pm5\ \%\ \text{of}\ V_\text{ex}$ for volumes equal to or greater than half nominal capacity $V$

• $\pm{\left(1.5\ \%\ \text{of}\ V +2\ \%\ \text{of}\ V_\text{ex}\right)}$ for volumes less than half nominal capacity $V$.

For syringes with a nominal capacity of $V\geqslant5\ \mathrm{ml}$, the tolerance amounts to

• $\pm4\ \%\ \text{of}\ V_\text{ex}$ for volumes equal to or greater than half nominal capacity $V$

• $\pm{\left(1.5\ \%\ \text{of}\ V +1\ \%\ \text{of}\ V_\text{ex}\right)}$ for volumes less than half nominal capacity $V$.

The values apply to the volume of water at a temperature of $T=\left(20\pm5\right)\ \mathrm{^\circ C}$ expelled from the syringe when the line circumscribing the end of the piston traverses a given scale interval.

The accuracy would depend on the brand and type of syringe in question.

If you need highly accurate amounts of a liquid, you'd be best to look at reusable syringes (Hamilton make some excellent ones) which are calibrated individually.

For most needs, the disposable medical syringes you mention are adequate, but not accurate for analytical purposes.

As an example, a 1 mL syringe often has markings which seem to indicate the ability to measure liquid to the nearest 0.01 mL, but in practice they are only accurate to the nearest 0.05 mL.

Generally speaking, the larger the syringe, the more 'accurate' you can be, as the volume by which the syringe is off by will be smaller as a percentage of the total volume.

You can test the accuracy (precision may also play a part) by taring an empty syringe on the balance, then syringing up a volume of liquid, before placing the filled syringe back onto the balance, as water has a density of roughly 1 g/mL, you can see for yourself how accurate the syringe is (assuming you have an analytical balance capable of reading to 3/4 decimal places).