Need Help Approximating How Much Hard Drive Space I Need For My DB Table.

In our SQL Server database we will have a table that will be populated with about 2000 records
per day. That is 2000 records per day for 5 days per week. Currently the computer we are using has about  50 gigabytes
of available hard drive space on it. We are concerned that maybe we will need a bigger hard drive,
based solely on the number of records entered into this table per day. The problem is I don't
know how to calculate how much hard drive space we need. I think I read that using varchar,
sql server 2005 really optimizes a database. Here is a typical example of data in our
database. I put dots on three lines between the first and last sample record to just
illustrate that there are many records in between.

Basically we only need 8 months of data at a time in the table and then we can purge
records older than 8 months.
Can someone help me approximate how much hard drive space I might need for 8 months of data,
given the following sample record in the database?

Sample: -->34.5               4.08        10.6       .0012


Sample Table in my DB just for illustration:

(PPsquare inch)  (Diameter)  (Weight gm)     (coeffOfSatFriction)

34.5                      4.08            10.6                .0012
.
.
.
21.7               3.54        6.22         .019