When buying air filters, we can be baffled by different air filter ratings like MERV and FPR (found on Home Depot filters). In order to figure out which filters have the same efficiency, we have to put MERV and FPR on the same denominator. We will look into FPR vs MERV rating, and include FPR to MERV chart as well as MERV to FPR chart to help you out.
Here are the two air filter ratings we have going to compare:
- MERV stands for Minimum Efficiency Reporting Value. This is the basic metric used to denote how well does an air filter capture different particles (based on the E1, E2, and E3 particle sizes standard). It was introduced back in 1987 under ASHRAE Standard 52.2 (American Society of Heating, Refrigeration and Air-Conditioning Engineers). This air filter scale goes from MERV 1 to MERV 16 or MERV 20 in some scales, with MERV 8, MERV 11, and MERV 13 being the most common ones for HVAC systems like furnaces and air conditioners. We can consider MERV as the official rating for air filters.
- FPR stands for Filter Performance Rating. This is an advanced metric used to denote how well does an air filter capture different particles, and how well it performs over time (including dust holding capacity and pressure drop). It was introduced by Home Depot as a scale for sub-HEPA air filters (that’s why you will see the FPR rating when shopping for filters at Home Depot). This air filter scale goes from FPR 4 to FPR 10 and is also color-coded (FPR 4 and 5 = Green, FPR 6 and 7 = Red, FPR 8 and 9 = Purple, FPR 10 = Black).
In short, MERV is not the same as the FPR rating. Basically, we are converting MERV 1-16 to FPR 4-10, and visa versa (FPR 4-10 to MERV 1-16). In the two charts below, we will see that only MERV 6, 7, 8, 9, 10, 11, 12, and 13 ratings can be converted to their respective FPR 4, 5, 6, 7, 8, 9, and 10 ratings.
Example: MERV 8 rating air filter for furnaces is the same as FPR 5 air filter rating. MERV 4 and MERV 14, for example, ratings don’t have their FPR rating equivalents.
Before we check the FPR to MERV chart and MERV to FPR chart, we need to understand what is the difference between MERV and FPR rating:
FPR vs MERV Rating: What Is The Difference?
FPR is a fairly new air filter rating. Compared to the FPR rating, the MERV rating is an established metric that’s more than 35 years old. We also know exactly what MERV means, but we don’t have full insight into how Home Depot designates FPR ratings to different filters.
Namely, different MERV ratings are assigned to air filters based on:
- Average particle size efficiency for 3 size ranges. Example: MERV 11 filter will capture up to 20% of 0.3-1.0 micron particles, up to 65% of 1.0-3.0 micron particles, and up to 3.0-10.0 micron particles.
As such it’s quite clear that different MERV-rated air filters are capable of. ASHRAE, however, uses only 1 metric to assign a MERV rating (average particle size efficiency). Compared to MERV, FPR uses 4 metrics to assign an FPR rating:
- MERV rating. It’s quite interesting that the MERV rating itself is a metric used as a factor in the FPR rating.
- Average particle size efficiency for 1 size range (0.3-1.0 micron, to be exact). These are the smallest particles that both FPR and MERV-rated air filters will be able to pick up. In the MERV scale, this metric is only used for higher MERV ratings (MERV 11, 12, 13, 14, 15, and 16).
- Pressure drop across the filter. Obviously, the pressure drop plays a big role in how efficiently will HVAC units using these FPR-rated air filters be able to run.
- Dust holding capacity. This is the ability of the filter to hold a different amount of dust; presumable, filters that can hold more dust and can last longer, have a higher FPR rating.
Why ‘presumably’ under the 4th metric?
Well, because Home Depot does not reveal how these 4 different metrics contribute to the overall FPR rating.
One thing is clear, however:
If you compare what the MERV vs FPR rating factor in, you can see that the MERV rating uses only 1 broad-based metric while the FPR rating uses 4 more specific-based metrics. That naturally means that the Filter Performance Rating (FPR) is superior to the MERV rating.
The one thing that Home Depot does reveal is how to convert the MERV rating to the FPR rating. Using their chart, we can create a MERV 6-13 to FPR 4-10 chart, and visa versa:
MERV Vs FPR Chart
|MERV Rating:||FPR Rating:|
|MERV 6||FPR 4|
|MERV 7||FPR 4|
|MERV 8||FPR 5|
|MERV 9||FPR 5|
|MERV 10||FPR 6 or FPR 7|
|MERV 11||FPR 8|
|MERV 12||FPR 9|
|MERV 13||FPR 10|
As you can see, FPR ratings are color-coded (low FPR 4 and FPR 5 are green, FPR 6 and FPR 7 are red, FPR 8 and FPR 9 are purple, and FPR 10 is black).
From this chart, you can see that some of the most commonly converted air filter ratings like:
- MERV 6 is equal to FPR 4.
- MERV 8 is equal to FPR 5.
- MERV 11 is equal to FPR 8.
- MERV 13 is equal to FPR 10.
The FPR scale end at MERV 13. That means that there are no designated equivalents for MERV 14, MERV 15, and MERV 16 in the FPR scale.
For easier use, let’s also show the FPR to MERV chart:
FPR Vs MERV Chart
|FPR Rating:||MERV Rating:|
|FPR 4||MERV 6|
|FPR 4||MERV 7|
|FPR 5||MERV 8|
|FPR 5||FMERV 9|
|FPR 6 or FPR 7||MERV 10|
|FPR 8||MERV 11|
|FPR 9||MERV 12|
|FPR 10||MERV 13|
With these MERV vs FPR and FPR vs MERV charts, you will be able to adequately convert MERV to FPR and FPR to MERV. This will give you a sense of what is the effectiveness of air filters with different ratings.