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Filter sizes, made simple

Got a filter to replace but not its part number? This guide shows you how to measure the old one, the standard sizes we hold, and how to order the right fit with confidence. Anything outside the standard range, we build to order.

Find your filter by size →

How to measure your old filter

Three quick measurements get you most of the way. You do not need specialist tools, a tape measure is enough.

  1. 1

    Measure height, width and depth

    Measure the filter face (height and width) and then the depth, in millimetres. Note them in that order: H x W x D.

  2. 2

    Note the frame or header type

    Check whether it has a cardboard, metal or plastic frame, and for bag and compact filters the header depth (the rigid front edge).

  3. 3

    Count the pockets (bag filters only)

    For bag or pocket filters, count the number of pockets and note the pocket depth. This affects airflow and fit.

Measure the face (height × width), then the depth.

A note on precision

Standard sizes are nominal, so a real filter usually runs a few millimetres under the stated size to fit its housing. You do not need to be exact to the millimetre. Get close and we will match the right standard size, or build to your exact dimensions if nothing standard fits.

Standard sizes

Sizes are shown in inches (nominal) with their millimetre equivalents. Standard depths are listed per type. We can make filters to any size, anything outside this we manufacture to order from the UK.

Panel filters

We can make panels any size, however, standard depths are 20 mm (1"), 45 mm (2") and 95 mm (4").

Panel filter sizes
Nominal (inches) Height (mm) Width (mm)
12x12292292
12x24292594
15x15368368
10x20241495
15x20368495
16x19394470
16x20394495
16x24394594
16x25394622
18x18445445
18x20445495
18x24445594
20x20495495
20x24495594
20x25495622
24x24594594

See panel filters in the shop →

Bag filters

Our default header depth is 20 mm, although 25 mm is common. Pocket depths can vary from as little as 100 mm up to 750 mm.

Bag filter sizes
Nominal (inches) Height (mm) Width (mm)
24x24592592
24x20592492
24x12592287
12x24287592
20x24492592
12x12287287
20x20492492
36x24892592
36x20892492
36x12892287
Pocket depth options
Depth (inches) Depth (mm)
12300
15350
20500
21535
24600
25635

See bag filters in the shop →

Help & support

Size questions, answered

What if my size isn't listed?
We manufacture bespoke sizes to order with no minimum quantity. Send us your dimensions and grade through the custom size request form, or call the team. [Final wording to be confirmed.]
Nominal or actual, which size do I order by?
Order by the actual measured size in millimetres wherever you can. The nominal inch size is a label, the actual size is what fits the housing. If you only have the nominal size, the table above gives the millimetre equivalent. [Final wording to be confirmed.]
How much tolerance is acceptable?
A few millimetres either way is normal, filters are made slightly under the housing size so they seat correctly. If you are unsure, give us the measured size and we will confirm the right fit. [Tolerance guidance from Colin to be confirmed.]
Can you match a competitor's filter?
Usually, yes. Give us the dimensions, grade and pocket count (for bag filters) and we will match it to a Jasun equivalent or build it to order. [Final wording to be confirmed.]
Bag filters: how do I count pockets?
Count the individual pockets (bags) across the header. Common counts are 3, 4, 6 and 8 pockets. The pocket depth is measured from the header to the tip of the pocket. [Final wording to be confirmed.]

Can't find your answer? Call 01278 452 277 or email our team.

Still not sure?

Reach out to the team. Send a photo of the old filter by email and we'll help you identify the right replacement.

Email us a photo → Call 01278 452 277