Measuring a custom panel filter correctly is essential to ensure a snug, airtight fit and optimal airflow — especially for HVAC, AHU, or machinery systems. Here’s a simple, step-by-step guide to getting accurate measurements 👇
🧰 What You’ll Need
Tape measure or steel rule (in millimetres if possible)
Notepad or phone to record measurements
Existing filter (if available) or the filter housing / frame
🔹 1. Measure the Existing Filter (if you have one)
If you’re replacing a filter, measure the actual filter, not the housing:
| Measurement | How to Measure | Example |
|---|---|---|
| Width (W) | Left to right across the face of the filter | 495 mm |
| Height (H) | Top to bottom across the face | 595 mm |
| Depth (D) | Front to back (thickness) | 48 mm |
✅ Tip: Always measure to the nearest millimetre (mm) — do not round up to “nearest inch” unless specified.
⚠️ Filters are often slightly undersized (by ~3–5 mm) to allow easy insertion into the frame.
🔹 2. If the Old Filter Is Missing — Measure the Housing
If the filter is missing, measure the internal space of the filter holding frame (where the filter slides in):
| What to Measure | Description |
|---|---|
| Opening width & height | Inside-to-inside of the frame (the actual slot or recess where the filter sits) |
| Depth of slot | Distance from front lip to rear stop inside the frame |
Then subtract 3–5 mm from the width and height to allow for a good fit (so the filter can slide in easily but not rattle).
🔹 3. Confirm Filter Type
Knowing the type helps you specify the right media and frame:
| Type | Description | Common Depths |
|---|---|---|
| Pleated panel filter | Cardboard or metal frame with pleated synthetic media | 22, 25, 48 mm |
| Pad / wire frame filter | Metal frame with loose or bonded media | 10–25 mm |
| Rigid / mini-pleat filter | Rigid plastic or metal box type | 48, 95, 150 mm |
| Carbon / odour filter | Activated carbon layer, usually heavier | 25–50 mm |
🔹 4. Check Airflow Direction
Look for arrow markings on the old filter — this shows airflow direction.
If missing, determine the airflow by:
Turning on the fan and feeling which way the air flows, or
Checking the blower / fan side vs. supply air side of the unit.
You’ll need this when installing the new filter.
🔹 5. Note Special Requirements
Include in your spec (especially when ordering custom sizes):
✅ Frame type (cardboard, galvanised steel, aluminium, plastic)
✅ Media grade (G4, M5, F7, HEPA etc.)
✅ Gasket or sealing strip (needed for airtight units)
✅ Handles or clips (if filters are frequently changed)
📏 Example Specification
Custom pleated panel filter
Size: 495 mm × 595 mm × 48 mm (W×H×D)
Frame: Galvanised steel
Media: G4 synthetic
Airflow: Left → right
Gasket: None
Dont hesitate to call the sales support team if you cannot be sure of ordering the exact product you require. Many times filters are damaged, missing or have been replaced with an incorrect filter in the past.
