EC2 Storage Requirement Calculator

Size EBS volumes per instance from OS, application and retained data, add growth headroom, and price the fleet.

About EC2 Storage Requirement Calculator

Retention is what turns a small daily write rate into the dominant term: 4 GB a day held for 45 days is 180 GB of steady state, far more than the OS and application together. Because EBS charges for provisioned rather than used capacity, headroom is a real cost — but volumes can be grown online with Elastic Volumes, so starting closer to the true requirement and expanding later is usually cheaper than sizing for year three on day one. Day-one utilisation is deliberately low on a retention-driven volume, so a monitoring alert set on percent-used will fire months later when the window fills — plan the alarm around the steady state, not the initial footprint.

Formula

EC2 Storage Requirement

volume size = (OS + application + daily data × retention days) × (1 + headroom); fleet cost = size × instances × price per GB-month.

retained data: Steady-state footprint once the retention window is full
headroom: Free space kept above the steady-state footprint
GB-month: EBS bills provisioned capacity, prorated per second

Worked example

With the default values below, EC2 Storage Requirement Calculator returns Volume Size per Instance of 294. Change any input above and every figure here is recalculated in your browser.

Inputs used

Operating system and packagesaccepts 0–4,096 GB: 30 GB
Application and dependenciesaccepts 0–16,384 GB: 25 GB
Data written and retained per dayaccepts 0–10,000 GB/day: 4 GB/day
Retention windowaccepts 0–3,650 days: 45 days
Free-space headroomaccepts 0–200 %: 25 %
Instances in the fleetaccepts 1–10,000 instances: 6 instances
EBS price per GB-monthminimum 0 USD/GB: 0.08 USD/GB

Results

Volume Size per Instance: 294 GB
Retained Data at Steady State: 180 GB
Fleet Provisioned Capacity: 1,764 GB
Fleet Capacity in Bytes: 1.60 TiB
Monthly EBS Cost: $141.12
Utilisation on Day One: 18.7%

Step by step

1Values used
2EC2 Storage Requirement
3Volume Size per Instance= 294 GB
4Retained Data at Steady State= 180 GB
5Fleet Provisioned Capacity= 1,764 GB
6Fleet Capacity in Bytes= 1,764,000,000,000.00
7Monthly EBS Cost= 141.12
8Utilisation on Day One= 18.7

Assumptions and limits

The result is derived only from the 7 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is EC2 Storage Requirement calculated?

volume size = (OS + application + daily data × retention days) × (1 + headroom); fleet cost = size × instances × price per GB-month. Retention is what turns a small daily write rate into the dominant term: 4 GB a day held for 45 days is 180 GB of steady state, far more than the OS and application together. Because EBS charges for provisioned rather than used capacity, headroom is a real cost — but volumes can be grown online with Elastic Volumes, so starting closer to the true requirement and expanding later is usually cheaper than sizing for year three on day one.

Why does EC2 Storage Requirement matter?

Day-one utilisation is deliberately low on a retention-driven volume, so a monitoring alert set on percent-used will fire months later when the window fills — plan the alarm around the steady state, not the initial footprint.

What values do I need to enter?

This calculator takes 7 inputs: Operating system and packages, Application and dependencies, Data written and retained per day, Retention window, Free-space headroom, Instances in the fleet, EBS price per GB-month. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.