DISCAS (Display Image Size) Calculator

Choose BDM (Basic Decision‑Making) for general messaging or ADM (Analytical Decision‑Making) when viewers must inspect fine detail. Enter the values you know, pick what you want to solve, and results update live.

BDM explained

BDM uses %‑Element Height. Common presets:
3 % = lecture slides • 2 % = financials • 1.5 % = dense spreadsheets.

ADM explained

ADM replaces %EH with vertical pixel resolution (720 / 1080 / 1440 / 2160). Use it for CAD, medical imaging, or anything where users must read small detail.

Quick reference (%EH & Closest Viewer)
Content type %EH preset Closest viewer ≈ 1.5 × IH
Lecture / key bullets3 %1.5 × IH
Standard PPT2.5 %1.5 × IH
Financial tables2 %1.5 × IH
Dense spreadsheets1.5 %1.5 × IH
Fine CAD (ADM)1 %1.5 × IH

Understanding DISCAS Calculations

The AVIXA Display Image Size for 2D Content in Audiovisual Systems (DISCAS) standard helps determine the appropriate display size or viewing distances for different types of content. This calculator implements two main viewing categories:

  • Basic Decision Making (BDM): This category is for content where viewers need to make simple decisions, grasp general information, or view passive entertainment. Examples include informational dashboards, presentations with large graphics, or general video viewing.
    • The key metric for BDM is Percentage Element Height (%EH). This refers to the height of the smallest critical element on the screen (e.g., a lowercase letter) expressed as a percentage of the total image height.
    • Common %EH values range from 1% to 3%. A larger %EH (e.g., 3%) means the content is relatively larger and easier to see from further away.
    • The simplified formula often used is: Image Height = Farthest Viewer Distance / (200 / %EH). Or, to find the Farthest Viewer: Farthest Viewer = Image Height * (200 / %EH). This calculator uses a factor of 150 for BDM instead of 200 based on a common interpretation for general presentation content to provide slightly larger text.
  • Analytical Decision Making (ADM): This category is for content where viewers need to inspect fine details, analyze complex information, or make critical judgments. Examples include detailed spreadsheets, CAD drawings, medical imaging, or command and control centers.
    • For ADM, the calculation is based on the display's Vertical Resolution (e.g., 720p, 1080p, 2160p/4K) and a factor related to visual acuity.
    • The principle is that a viewer with normal (20/20) vision can distinguish detail that subtends 1 arcminute of their field of view. This translates to being able to resolve approximately 3438 pixels per radian.
    • The formula used is: Image Height = Farthest Viewer Distance * Vertical Resolution / 3438. Or, to find the Farthest Viewer: Farthest Viewer = Image Height * 3438 / Vertical Resolution.

The "Solve for" option allows you to calculate Image Height, Farthest Viewer, % Element Height (for BDM), or Vertical Resolution (for ADM) when the other relevant parameters are known. The Closest Viewer distance is generally recommended to be no closer than 1.5 times the image height for comfortable viewing, though this is a guideline and not part of the core DISCAS calculation itself.