How do I calculate database growth 12 months from now?

I often get asked a question similar to that; I need to figure out how to calculate what my database size will be 12 months down the road, or 24 months, or 36 months?  But how do I do that?

There is a simple formula we can use to calculate this; however in order to do it we need to know few key values.

• What is current size? (CurrentSize(mb))
• What is the expected monthly growth in percent? (ProjectedGrowthPerMonth(%))
• How many months we want to know growth for? (NumberOfMonthsToProject)

So lets take this formula and try to calculate the growth for a database.  Lets say we have a database that is 10240MB and it is projected to grow by 10% per month.  What would be its size in 12 months from now?

NewSize (MB) = 10240MB * [(1 + 10%) ^ 12] = 10240MB * [1.10 ^ 12] = 10240MB * 3.14 = 32153MB approx.

We can verify our final value by doing manual calculation like so …

Month	Size @ Start	Growth	Final Size
1	10,240.00	1,024.00	11,264.00
2	11,264.00	1,126.40	12,390.40
3	12,390.40	1,239.04	13,629.44
4	13,629.44	1,362.94	14,992.38
5	14,992.38	1,499.24	16,491.62
6	16,491.62	1,649.16	18,140.78
7	18,140.78	1,814.08	19,954.86
8	19,954.86	1,995.49	21,950.35
9	21,950.35	2,195.03	24,145.38
10	24,145.38	2,414.54	26,559.92
11	26,559.92	2,655.99	29,215.92
12	29,215.92	2,921.59	32,137.51

We can see the final size is approx same as one calculated above. Most likely difference occured because I rounded off the “3.14”; where as table above is generated via Microsoft Excel handling the rounding for me.