Hilliness is best measured by some system that describes the climb in relation to the distance, this is easily done by dividing total climb by total distance. I prefer imperial so go for ft/mile, but obviously conversion is simple. To give some idea in lieu of experience the following is a ready reckoner.
0 ft/mile – Only if you can walk on water.
10 ft/mile – What most would call a pan flat route, eg somewhere out in Lincolnshire.
30 ft/mile – Mild undulation, eg somewhere in Notts.
50 ft/mile – Mild hills, a trip out to the Peak where you are not going up every hill you spy
60 ft/mile – Stoke ‘Tour of Britain’ Sportive
70 ft/mile – A fairly concerted effort to make the route hilly, a visit to Crich and Winster woukd probably achieve this
90 ft/mile – A mad though uncontrived trip zigzagging up either side of the Derwent valley taking in every hard climb.
110 ft/mile – The limit of what I can currently roll out in the Peak from home (I can’t make it hillier!). Contrived and ignoring any prolonged flat. Home legs are as per ‘hilly night’ And Crich is visited 2 or 3 times in contrived and masochistic loops. You are either going up or down, the route to supreme fitness
120 ft/mile – Autumn Epic
 Audax folk are continental and go for metres/km
So I thought it may be handy to add the 'Hillometer' rating to my blog as well so I can measure how much hill work I am getting and factor this weak point into my training.