When specifying the size (diameter) of hydraulic hoses it is vital that the right calculations are done to obtain the correct size of hose. Too narrow and the pressure in the hose will cause damage to the seals and increase the pressure of the liquid flowing into a chamber. Too wide and there will not be sufficient pressure in the hose for the liquid to flow at the right rate – it will move too slowly and may even back up, never reaching the intended destination. The traditional way of determining the correct hose size is to use nomograms and a ruler or a calculator and some complicated formulae. As with any process where human input is required there is scope for human error, which could be very costly to correct if a custom piece of machinery has been built on the basis of incorrect hose size calculations. Sergiy Sydorenko of Insane Hydraulics, has built an online interactive tool for hydraulic designers and engineers that will be invaluable when deciding on the correct hydraulic hose size. It can be found here for those who are interested in taking a little shortcut on their calculations, or for those who want an accurate resource against which to check their manual calculations. The interactive tool allows you to specify the flow rate and speed needed, and then uses these numbers to define the correct size of hydraulic hose. Annotations on the tool show the maximum recommended velocities for different types of line, so if you need to adjust the flow rate to make it work for a particular size of line this is also possible using the tool – it will tell you the right flow rate for any size of hydraulic hose. This is one online tool that should be in the bookmarks of every hydraulic engineer.