Data Engineering

Data Storage Growth Calculator

Size and monthly cost projected to five years, with compression, indexes, replicas and retention applied.

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How to use this tool

  1. Set rows per day and an average row size. A size can be written as 480 bytes, 1.2 KB or 1.2 KiB.
  2. Add the compression ratio, index overhead and replica count your platform actually applies.
  3. Add a retention window. Without one the projection grows forever, which is itself the finding.
  4. Select Project growth, and read the row where the note says retention has kicked in — that is the steady-state size.

What storage growth calculator does

Rows times bytes times days is the estimate everyone does in their head, and it is wrong by a factor of three or four in either direction. Compression pulls it down, indexes push it back up by roughly a third, replication multiplies whatever is left, and retention is the only thing that stops the total climbing forever.

All four are applied here and each is reported separately, so you can see which one is actually driving the number. The single most useful output is usually not the five-year total but the steady state: with a retention window set, the table stops growing at a size you can name, and a design that has no such number is the finding rather than the total.

Frequently asked questions

KB, MB, GB and TB are powers of 1000, which is what storage vendors and cloud bills use. If you want powers of 1024, write KiB, MiB, GiB or TiB and they will be read that way.

Thirty percent is the default and is a reasonable starting point for a transactional table with a handful of indexes. A heavily indexed table can exceed a hundred percent, meaning the indexes are larger than the data. A columnar table with no secondary indexes is close to zero.

Because the retention window has filled. Once you are deleting as much per day as you are adding, the table is at steady state and stops growing. That steady-state size is the number worth taking to a capacity conversation — not the five-year total, which only applies if you never delete anything.

Growth compounds on the daily arrival rate, so the steady state creeps upward too. The projection integrates the growing rate across each period rather than applying growth once at the end, which matters over three years or more.