How is the Hardware sizing done for SAP HANA

Dear friends,

Excuse me if it is not in the correct forum.

We have got a current application running on a customised erp solution of which the database size is around 5 GB and 100 users.

and now our group is adding a new steel plant which will add another 50 users.

We have signed up with sap very recently and have asked for HW configuration from the implementation partners. we got different sizing from different implementers which has confused me so is there a general rule of thumb or some body can guide me on this.

Thanks and regards

Arun Kumar Menon