What is the accuracy of medical syringes?
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.