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MERV Rating Chart

The MERV 1 to 16 scale from ASHRAE 52.2, grouped by what each range of filters mainly captures. A higher MERV catches smaller particles but can add airflow resistance.

Ref HV-0047ASHRAE 52.2

Draft, open for review. Check every value against the governing standard and the manufacturer’s data before use.

What it is

MERV (Minimum Efficiency Reporting Value) is a 1 to 16 rating for air filters, set by testing under ASHRAE 52.2. The test measures how well a filter removes particles in three size ranges:

E1: 0.3 to 1.0 µm (smoke, bacteria, fine combustion particles)
E2: 1.0 to 3.0 µm (fine dust, mold spores, some pet dander)
E3: 3.0 to 10.0 µm (pollen, dust mites, larger dust)

The MERV is set by the filter's lowest efficiency during the test in each range. Low MERV filters are graded mostly on large particles. High MERV filters must also catch the E1 range.

How to read it

Find the MERV on the filter frame or carton. It should state ASHRAE 52.2 as the test method.
A rating such as MERV 13-A or MERV-A means the filter was also tested after conditioning (Appendix J). That rating shows performance without the help of an electrostatic charge.
Other rating systems (for example MPR or FPR) are brand scales, not MERV. ISO 16890 is a different international method. They do not convert one-for-one.

MERV group chart

MERV	Typical construction	Mainly captures	Typical use
1–4	Fiberglass, washable or thin panel	Large dust, lint, carpet fibers	Equipment protection
5–8	Pleated, 1–2 in	Pollen, dust mites, mold spores, larger dust	Standard residential and light commercial
9–12	Pleated or deep media	Adds more of the 1–3 µm range, such as fine dust	Better residential, commercial
13–16	Deep media, bag or box	A large share of 0.3–1 µm particles, rising with MERV	Commercial, healthcare, high-IAQ projects

HEPA filters are rated under other methods and are not on the MERV scale.

Key points

Higher MERV usually means higher pressure drop. A 1 in MERV 13 filter in a return built for fiberglass can starve the blower. Check the equipment's allowed static pressure.
Deeper filters (4 or 5 in media) usually give the same MERV with less resistance and longer life.
A filter only works if air goes through it. Seal gaps around the frame and rack.
Codes and green building programs may set a minimum MERV. Check the project documents.

Common mistakes

Treating MPR or FPR numbers as MERV values.
Upgrading to a high MERV filter without checking static pressure.
Ignoring bypass around a loose filter.

Governing standards: ASHRAE 52.2 (test method and MERV); ASHRAE 62.1 and 62.2 and the adopted mechanical and energy codes (where a minimum MERV applies); equipment manufacturer data on pressure drop.

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.

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