Calculate theoretical slot open area for Johnson screens and wedge wire screens. Reverse-calculate the slot width and estimate clear opening area for a flat panel or cylindrical screen.
Enter your inputs, then select Calculate.
Local theoretical open area
Local open area = s / (s + w) × 100%
Reverse slot width = w × f / (1 − f), where f is the target open-area fraction.
Net opening area = active region × f − known additional blocked opening area.
Effective overall open area = net opening area / overall surface × 100%.
For a sheet, active area uses the length and width after subtracting both end and side margins. For a cylinder, it uses π × screening-surface diameter × active length. Cylinder end faces are excluded.
This is a repeating-slot geometric estimate. Edge slot counts, slot tolerances, seams and support geometry may require a drawing-based calculation. Open area does not specify filtration efficiency, pressure drop or flow capacity.
Slot width describes the surface opening. Particle retention also depends on particle shape, orientation and operating conditions.
Use the diameter at the slotted screening surface. Select the inside or outside screening surface according to the actual screen construction.
Only known blocked opening area is deducted. A support's projected surface area can overlap both wire faces and slots, so the whole support area is not automatically a loss of open area.
Products
Resources
Contact us
Location:
Hi-Tech Industrial Zone, Hengshui,
Hebei, China, 053000
Contact:
+86 133 1308 7837
Email: info@alloyfilter.com
COPYRIGHT © 2026 FILTALLOY TECHNOLOGY LIMITED
