ExactFilterFit CALIPER & RFID SPEC DB
← Back to Master Cross-Reference Directory • Category: HVAC Nominal-vs-Actual Sizes • Nominal Spec: 16x20x4
HVAC Nominal-vs-Actual Sizes

16x20x4 Air Filter Actual Size Chart: 3.63" Slim vs. 4.38" Honeywell/Lennox Cabinet

A filter labelled 16x20x4 can be one of two very different cartridges. Standard pleated 4-inch filters (Nordic Pure, Mann+Hummel and most generics) are about 15-1/2" x 19-1/2" x 3-5/8" to 3-3/4" deep, while Honeywell F100/F200-style media cabinets (also copied by Lennox, Bryant and Carrier) take a 15-7/8" x 19-7/8" x 4-3/8" cartridge. Put a 3-5/8" filter in a 4-3/8" cabinet and unfiltered air bypasses the media.

⚠ CRITICAL FIT RULE: Measure the depth of your old filter. If it is about 4-3/8" (4.38"), buy a Honeywell FC100A1003-compatible cartridge (or a brand's '16x20x5 Honeywell replacement'). If it is about 3-5/8" to 3-3/4", a standard pleated 16x20x4 is the correct fit.
Verified Reddit Fit Complaint: r/hvacadvice: 'Apparently the big numbers on filters are just suggestions' (16x20x4, 4-1/4" old vs 3-5/8" new)
Verified Reddit Fit Complaint: r/hvacadvice: 'I think my furnace filter is too small' (standard 3-5/8" vs Honeywell 4-3/8")

Side-by-Side Exact Caliper & RFID Compatibility Matrix

Measured to 1/8" (0.125") Tolerance
OEM Brand & Model Exact Caliper Size (In) MERV / NSF Cert Slot Fit / RFID Chip Status OEM Price Verified Multi-Pack Match Direct Spec Links
Honeywell FC100A1003 (OEM, MERV 11)
Group: Honeywell F100 / F150 / F200 / F25 / F35 media cabinets (e.g. F100F1004, F200E1003)
 15.875" x 19.875" x 4.375"
15-7/8" x 19-7/8" x 4-3/8"
 MERV 11 Deep cabinet: 4-3/8" depth required $84.99 (AllFilters, Oct 2026) OEM 2-pack on Amazon
About $53.00 / 2-pack (Amazon, 21 Oct 2026) Save Check live price
Verify Exact Fit → Amazon
Filtrete 16x20x4 MPR 1550 / MERV 12
Group: Honeywell-style 4-3/8" cabinets (near fit, 4.31" deep)
 15.88" x 19.88" x 4.31"
15-7/8" x 19-7/8" x 4-5/16"
 MERV 12 (MPR 1550) Within 1/16" of Honeywell depth Honeywell FC100A1003 reference: $84.99 Filtrete MPR 1550 2-pack (Amazon B086DYVPW2)
About $36.19 / 2-pack (Amazon, 22 Oct 2026) Save Check live price
Verify Exact Fit → Amazon
Nordic Pure 16x20x4 pleated (MERV 8 / 13)
Group: Standard 4" filter racks and slim media cabinets ONLY
 15.5" x 19.5" x 3.63"
15-1/2" x 19-1/2" x 3-5/8"
 MERV 8 / MERV 13 Will sit short in a 4-3/8" Honeywell cabinet N/A (standard size) Nordic Pure 16x20x4M13-6
Check live price Save Check live price
Verify Exact Fit → Amazon
Mann+Hummel 16x20x4 MERV 8
Group: Standard 4" filter racks; does not replace 4-3/8" or 5" filters
 15.5" x 19.5" x 3.75"
15-1/2" x 19-1/2" x 3-3/4"
 MERV 8 (MPR 600) Standard 4" depth N/A (standard size) Mann+Hummel 16x20x4 2-pack (Target)
$38.95 / 2-pack (Target sale price) Save Check live price
Verify Exact Fit → Amazon

Frequently Asked Fit & Bypass Questions

Q: Why is my 16x20x4 Honeywell filter 4-3/8 inches thick?
Honeywell pioneered deep-pleat media cabinets and sized its cartridges at 15-7/8" x 19-7/8" x 4-3/8". Lennox, Bryant and Carrier cabinets were often built to the same spec, so a '4-inch' label there really means 4-3/8".
Q: Can I use a standard 3-5/8" 16x20x4 filter in a Honeywell F100 or F200 cabinet?
It will physically slide in, but it leaves roughly a 3/4" gap in depth and about 3/8" on the face, so air can bypass the media. Buy an FC100A1003-compatible cartridge instead, or a brand's '16x20x5 Honeywell replacement', which is the 4-3/8" size.
Q: How do I tell which 16x20x4 I need?
Measure your old filter's depth with a tape measure. About 4-3/8" means Honeywell-style; about 3-5/8" to 3-3/4" means standard pleated. You can also check the cabinet label (for example Honeywell F100F1004) and match the part number.

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