Cylinder vs rectangular air purifier filters

Four layouts, two independent comparisons

Choose Cylinder, Rectangle, Double rectangle or Double cylinder on either side, then use that side’s model dropdown. Cylinder offers Mijia Smart Air Purifier 6 and Dyson HushJet; Rectangle offers Sharp FP-J80E-H and Treeow T3Pro; Double rectangle offers Sharp FX-S120E-H and FX-S82E-L. Double cylinder currently offers Mijia Max. Each side has its own dimensions and reset button. Switching designs or models restores previous edits for that model on that side; reset restores only the selected model’s defaults. Drawings share a scale based on overall housing height so different sizes stay comparable.

The defaults are Mijia Smart Air Purifier 6 for Cylinder, Sharp FP-J80E-H for Rectangle, Sharp FX-S120E-H (S120) for Double rectangle, and Mijia Smart Air Purifier Max for Double cylinder. Model presets combine published dimensions with explicitly labelled geometry estimates; they do not reconstruct every internal component.

Filter face area

Housing dimension captions use H for overall height, W for width, and D for depth. In the formulas below, A denotes overall height to distinguish it from the cylindrical Filter height H input. Filter diameter D is a separate, explicitly labelled dimension; it does not mean housing depth. Enter filter diameter and per-filter height directly on either cylinder type. Circular presets use a W × W housing footprint, so their housing depth equals width. A cylindrical filter can be narrower than the housing.

Layout	Filter face area	Airflow in the sketch
Cylinder	π × filter diameter × filter height	Side intake through the filter; upward discharge.
Rectangle	Filter face width × filter height	Back intake; discharge from the upper outlet.
Double rectangle	2 × filter face width × filter height	Two side intakes; discharge toward the front and upward.
Double cylinder	2π × filter diameter × filter height, entered per filter	Upper and lower cylindrical filters feed two central impellers; discharge from the middle.

Two cylinders with the same D and per-filter H have twice one cylinder’s face area, but also require twice its total filter height. Splitting a fixed total filter height between two equal cylinders does not increase total face area. The Max preset has its own dimensions, so its result differs from the Mijia 6 preset.

Rectangular filter width and height are entered separately from housing dimensions. The S120 uses 23.5 × 43.5 cm per filter face. The FP-J80 uses its published replacement-filter face dimensions. Treeow T3Pro still uses a full housing-face estimate. The FX-S82 uses an estimate derived from the S120’s housing-to-filter allowances; its actual filter dimensions have not been established. Changing housing dimensions alone does not change the entered filter sizes. Real frames and seals reduce the active filtering area within the filter’s outer dimensions.

These are calculated external filter face areas, not unfolded pleated media areas. Cylindrical top and bottom surfaces are excluded. A panel contributes its face area once; counting its front and back does not double it.

Dark dotted 3D wireframes show each design’s housing envelope, including front, back and connecting depth edges. Cylindrical filters are drawn as hollow tubes with open centers. The core opening and ring thickness are schematic; no inner diameter is assumed in the face-area calculation.

Fan size, estimated thickness and noise

For circular designs, fan diameter follows filter diameter D as a modelling assumption. The Fan size · height slider changes axial fan-compartment height/thickness, not diameter. Its maximum is A − H for Cylinder and A − 2H for Double cylinder. The second limit subtracts both filters. Reducing available space automatically caps the slider; increasing space makes more height available without changing the chosen filter dimensions. Any unused height is shown as unallocated space.

For Double cylinder, the slider controls the combined central fan compartment; half its selected height is allocated to each impeller in the sketch. Circular fan-envelope area is πD²/4 per impeller. The displayed sum for two impellers is not equivalent to one larger fan. Actual impeller dimensions were not established from the cited specifications.

The single rectangle shows filter width × filter height as an ideal available fan envelope, not the blade area of one circular fan. The Sharp double rectangle’s actual fan dimensions remain unspecified. Both rectangular drawings include an orange box marking the fan location. Its size and position, along with the drawn filter-stack thickness, are schematic rather than measured. Stack thickness is not used to invent additional face area. Outlet direction does not determine fan diameter or blade area.

Subtracting the published cylindrical filter heights from overall housing height gives a residual fan-space estimate, not measured fan thickness. It also includes the base, covers, gaps, ducts, electronics and other structures. For Max, dividing the residual equally between two impellers is an illustrative allocation, not a physical measurement.

A larger usable fan may run at lower speed and sound softer at the same airflow. Noctua’s manufacturer comparison illustrates noise reductions achieved by lowering speed for equal airflow; it does not test these purifier layouts. Noctua’s inlet-spacing tests also show that obstructions and resistance affect noise. The calculator does not derive dB values or rank model noise from geometry alone.

Front exhaust arrows point toward the viewer, diagonally down-left in the drawing’s perspective. They do not depict a sideways outlet. The double rectangle’s front/up airflow follows the illustrated comparison layout; an equal 50/50 split has not been established for the Sharp preset, so no outlet percentages are asserted.

Preset sources and limits

Cylinder default: Mijia Smart Air Purifier 6

Xiaomi Singapore’s housing specification lists 250 × 250 × 555 mm. Xiaomi’s replacement-filter specification lists Ø210 × 293 mm for AFEP8TFM25-GL, compatible with Mijia Smart Air Purifier 6. The preset therefore uses housing width 25 cm, overall height 55.5 cm, filter diameter D = 21 cm, and filter height H = 29.3 cm. The fan-height slider defaults to its 55.5 − 29.3 = 26.2 cm maximum, an estimate of non-filter space rather than measured fan thickness. Calculated filter face area is ≈ 1,933 cm².

Cylinder option: Dyson HushJet Purifier Compact HJ10

Dyson Singapore’s product description gives 230 mm width and 469 mm height, while its specification table lists 230 × 230 × 470 mm. The preset follows the description and supplied dimensions: 23 × 23 × 46.9 cm in width × depth × height order.

The filter preset uses ≈ 22.2 cm diameter × 28.2 cm height, from Joshin’s listing for the genuine Dyson 975009-01 filter, which specifies an approximate filter body size of 282 × 222 × 222 mm. Dyson Japan confirms that part 975009-01 fits the HushJet SP01. These are retailer-listed regional filter dimensions, not measurements made for this comparison.

Dyson Singapore lists a different electrostatic + formaldehyde filter, part 975008-01, without dimensions on that page. Its dimensional equivalence to 975009-01 has not been established, so the calculator labels the regional dimensions as an estimate for the Singapore model.

Using this preset, the calculated fan-height allowance is 46.9 − 28.2 = 18.7 cm, and the external filter face area is ≈ 1,967 cm². These are geometry estimates, not Dyson performance ratings or measured fan dimensions. The drawing uses the shared hollow-cylinder schematic rather than reproducing the HushJet nozzle or internal construction.

Double cylinder default: Mijia Smart Air Purifier Max

Xiaomi Singapore’s housing specification lists 290 × 290 × 760 mm and two filters. Xiaomi’s Max filter specification lists Ø241 × 200 mm for AFEP7TFM34-GL, supplied as a pair. The preset uses 29 × 29 × 76 cm housing dimensions and two Ø24.1 × 20 cm filters. Calculated combined curved filter face area is ≈ 3,029 cm².

The filter-height input is H = 20 cm per filter. The fan-height slider defaults to its 76 − 2 × 20 = 36 cm total maximum, or ≈ 18 cm per impeller if allocated equally. This includes all non-filter height and must not be treated as a measured fan dimension. Xiaomi’s product page describes a single fan drive with dual impellers and upper/lower filters. The diagram shows the middle exhaust and two impellers schematically; their estimated diameters follow D = 24.1 cm each.

Double rectangle default: Sharp S120

The preset uses the Singapore FX-S120E-H, matching the model in the site’s comparison. Sharp Singapore’s specification and layout give housing dimensions 333 mm wide × 578 mm high × 330 mm deep and describe filters on both sides of the fan. The preset stores these as 33.3 × 33 × 57.8 cm in width × depth × height order.

The filter preset uses 23.5 cm wide × 43.5 cm high per side, giving 2 × 23.5 × 43.5 ≈ 2,045 cm² total face area. CleanFilter’s compatible replacement listing gives 435 × 235 × 35 mm for the HEPA filter and 435 × 235 × 10 mm for the carbon filter. The reader confirmed the 23.5 cm face width. These supplier dimensions are used as a calculated estimate, not a Sharp manufacturer measurement; the 43.5 cm height remains supplier-sourced. Layers sharing one face are counted once. Fan dimensions remain unverified. The forward/upward split is a simplified airflow illustration; no measured 50/50 ratio is claimed.

Rectangle default: Sharp FP-J80E-H

Sharp Singapore’s FP-J80E-H specification gives 416 mm wide × 728 mm high × 291 mm deep. The preset uses 41.6 × 29.1 × 72.8 cm in width × depth × height order. Sharp Vietnam’s COCORO Life store lists the FZ-J80HFE replacement filter with product dimensions 38 × 250 × 450 mm, compatible with FP-J60E-W and FP-J80EV-H. The calculator uses a 25 cm wide × 45 cm high face, giving ≈ 1,125 cm², with 3.8 cm thickness recorded as source information. Sharp’s regional operation manual identifies the same FZ-J80HFE filter part. These are filter product dimensions, not packaging dimensions; frames reduce the active media area.

Sharp’s operation manual, EN-4 locates the rear intake/filter stack and upper front/back outlets. The sketch shows rear intake and an upward discharge from the upper outlet, rather than a forward outlet halfway down the housing. The orange fan box and filter-stack thickness indicate component locations schematically; their actual dimensions are not established here.

Rectangle option: Treeow T3Pro Air Purifier

The supplied Treeow T3Pro listing was accompanied by housing dimensions of 365 × 365 × 860 mm, entered as 36.5 × 36.5 × 86 cm in width × depth × height order. These dimensions were supplied by the reader and have not been independently verified from the listing. The full housing-face filter estimate is 36.5 × 86 = 3,139 cm². Actual T3Pro filter dimensions, fan dimensions and internal airflow have not been established; the drawing uses the comparison’s rectangle schematic. Dimensions for the older T3 have not been substituted for the T3Pro.

Double rectangle option: Sharp FX-S82E-L

Sharp Singapore’s specification gives 285 mm wide × 525 mm high × 285 mm deep and describes dual-side filtration. The preset uses 28.5 × 28.5 × 52.5 cm in width × depth × height order. Its filter estimate assumes the same total housing-to-filter allowances as the S120: 33 − 23.5 = 9.5 cm across the housing depth, and 57.8 − 43.5 = 14.3 cm vertically. Applying these allowances gives 28.5 − 9.5 = 19 cm filter width and 52.5 − 14.3 = 38.2 cm filter height per side. Total calculated face area is 2 × 19 × 38.2 ≈ 1,451.6 cm². These allowances include all space outside the filter face, not measured physical wall thickness; if split evenly, they correspond to 4.75 cm at each depth edge and 7.15 cm at top and bottom. Sharp Singapore identifies its replacement dust filter as FZ-S80H2E and deodorizing filter as FZ-D40D2E. Physical filter dimensions have not been established, so these inputs are explicitly labelled as estimates based on the S120 allowances. The assumption defines the model defaults; subsequent filter and housing edits remain independent. Filter thickness, fan dimensions and discharge arrows remain schematic.

Shared assumptions

None of the presets includes pleat geometry, seals or blocked filter faces. Editing a preset creates a custom geometry; its source links describe the baseline product, not your modified dimensions.

More face area alone does not establish higher CADR, quieter operation or better particle removal. See the air purifier comparison for sourced performance results and their fan settings.