Calculate X-ray grid ratio, lead-strip height, or clear interspace width. Compare mAs using known Bucky factors for unchanged test conditions. Educational calculations do not select a clinical grid or exposure protocol.

Compare lead-strip height with the clear interspace width.

Educational calculation only. Grid ratio alone does not determine exposure factors or the grid appropriate for a patient; follow the equipment and department protocol.

Width between adjacent strips, excluding the lead strip itself.

Grid Ratio Formula

The following formula is used to calculate the Grid Ratio. 

GRD = HLS / DS
  • Where GRD is the Grid Ratio
  • HLS is the height of lead strips, converted to the same unit as DS 
  • DS is the clear interspace width between strips, excluding lead strip width 

To calculate a grid ratio, divide the height of the lead strips by the clear interspace width, using matching units. Grid ratio alone does not determine a Bucky factor or the grid appropriate for a patient; use a validated equipment and department protocol.

How to Calculate Grid Ratio?

The following example problems outline how to calculate Grid Ratio.

Example Problem #1:

  1. First, determine the height of lead strips (in).
    • The height of lead strips (in) is given as 5.
  2. Next, determine the distance between strips (in).
    • The distance between strips (in) is provided as 6.
  3. Finally, calculate the Grid Ratio using the equation above: 

GRD = HLS / DS

The values given above are inserted into the equation below and the solution is calculated:

GRD = 5 / 6 ≈ 0.8333 : 1 (an arithmetic example, not a typical clinical grid geometry)

Example Problem #2: 

For this problem, the variables required are provided below:

height of lead strips (in) = 6

distance between strips (in) = 10

Test your knowledge using the equation and check your answer with the calculator above.

GRD = HLS / DS = ?