The SPH method uses a first-order integration scheme to march in
time. A stable SPH solver time step, 
, is computed according to:
 | (2–47) |
where:
is a coefficient defined by Time Step
Factor, which is a method parameter with a default value of 0.25. 
is the material speed of sound defined by Sound
Speed, which is a method parameter. 
is the smoothing length for the selected smoothing kernel.
There is an additional criterion for high-viscosity flows when calculating the SPH time step:
 | (2–48) |
Where:
is the fluid density.
is the fluid dynamic viscosity.- is the smoothing length for the selected smoothing kernel.
Therefore, the SPH solver time step is given by the minimum value between the two calculations.
Note: If a fixed time step is selected, this value will overrule the calculations above.