How much time does a sand clock last?

How much time does a sand clock last?

Well,sand clock duration depends on 3 main factors:

1.  The grains(micro sand beads) size,fine sand or coarse sand.

2.  The size of the connecting hole in the middle of a hourglass where the sand go through.

3.  The Size of the sandglass itself.

Let me explain,for example we prepared empty sandglass size approx. 5cm x Height 10cm,if we use fine sand and a small connecting hole,this sandglass can last probably 15 minutes,but if we use a coarse sand with a big hole,it can only last for 1 minute.combine these two factors,we use fine sand with a bigger hole,it may last 7 minutes or even 10 minutes.But with 10cm height,the sandglass do have a maximum limit of time-keeping.so if we want a sand clock last 30 minutes,we will need a bigger one anyway.