16x25x5 Air Filter: Actual Size, MERV Guide & Replacement
Nominal vs actual size
| Nominal (order this) | 16 x 25 x 5 in |
|---|---|
| Actual | 15.75 x 24.75 x 4.38 in (Honeywell/Carrier family; Filterbuy spec, two other cuts exist) |
A 5-inch media-cabinet size, the boxed housing with a hinged door on the return duct of a central furnace, heat pump or AC air handler. One filter serves both heating and cooling. The size is set by the cabinet, which is often a different brand from the furnace, so read the cabinet's label or part number. Filters are deliberately cut smaller than their nominal label so they slide into the slot; length and width typically run about 1/4 to 1/2 inch under nominal. Actual sizes vary slightly by brand, so compare against the small print on your old frame.
How to measure
- Turn the system off at the thermostat (and the service switch) before pulling the filter.
- Read the frame first: the large print is the nominal size (what you order); small print, if present, is the actual size.
- If there is no label, measure length, width and depth edge to edge with a tape measure.
- Round each measurement up to the nearest whole inch to get the nominal size (e.g. 19.5 x 24.5 x 0.75 → 20x25x1).
- No old filter? Measure the filter slot or cabinet opening the same way.
- Note the airflow arrow: it should point toward the furnace or blower.
MERV 8 vs 11 vs 13
| MERV | Minimum capture (EPA / ASHRAE 52.2) | Good for |
|---|---|---|
| 8 | ≥20% of 1–3 µm, ≥70% of 3–10 µm | Basic dust, pollen, lint; the minimum EPA Indoor airPLUS requires |
| 11 | ≥20% of 0.3–1 µm, ≥65% of 1–3 µm, ≥85% of 3–10 µm | A step up for pets and allergies |
| 13 | ≥50% of 0.3–1 µm, ≥85% of 1–3 µm, ≥90% of 3–10 µm | EPA's recommended level for fine particles (PM2.5), if your system can accommodate it |
EPA notes that higher-MERV filters tend to restrict airflow, and recommends using the highest rating your system fan and filter slot can accommodate. Most systems handle MERV 13 if the filter is replaced frequently. Thin 1-inch slots are the most restrictive; deeper 4-inch media filters generally create less static pressure. Weak airflow from vents, a system that runs longer, or a filter that bows are signs to step down a grade or ask an HVAC technician.
How often to replace
ENERGY STAR: check your filter every month and change it when it looks dirty, at least every three months. Pets, dust, renovations and heavy heating/cooling seasons can mean more frequent changes.
Equivalent & nearby sizes
There is no exact substitute for a different size: length, width and depth must all match. These nearby sizes are commonly confused with 16x25x5:
FAQs
What is the actual size of a 16x25x5 air filter?
It depends on the cabinet. Filterbuy makes three cuts under the 16x25x5 name: 15.75 x 24.75 x 4.38 inches for Honeywell, Carrier, Bryant, Lennox, Emerson and White Rodgers cabinets; 15.63 x 24.13 x 4.88 for Trion Air Bear, GeneralAire, Skuttle and Ultravation; and 15.38 x 25.5 x 5.25 for Amana, Goodman, Coleman, York, Nordyne, Gibson, Maytag and Five Seasons. They aren't interchangeable.
Which 16x25x5 do I need?
Go by the brand and part number on the filter cabinet, not the furnace. Filterbuy lists Honeywell FC100A1029 and FC200E1029, Carrier/Bryant HCF16-10 and Lennox X6670 for the 4.38-inch cut; Trion 255649-105 and GeneralAire GA100A29 for the 4.88-inch cut; and FS1625, M1-1056 and MU1625 for the 5.25-inch cut. Filterbuy notes Payne, Day & Night and BDP built cabinets in more than one size, so match the part number there.
No label and no old filter. How do I tell which one fits?
Measure the depth of the slot. Per Filterbuy, under about 4 1/2 inches is the 15.75 x 24.75 x 4.38 cut, about 4 7/8 inches is the 15.63 x 24.13 x 4.88 cut, and over 5 inches is the 15.38 x 25.5 x 5.25 cut. Turn the system off before opening the cabinet door.
Can I use a 16x25x4 in a 16x25x5 cabinet?
No. Filterbuy says the missing inch leaves a gap so air goes around the filter, and you can't stack thinner filters to fill the depth. EPA also says a filter must fit snugly so air doesn't leak around it.
How often should I replace a 16x25x5 filter?
Filterbuy says most homes replace a 16x25x5 every 6 to 12 months, against about 90 days for a 1-inch filter, because the deep pleats hold much more dust. ENERGY STAR says to check your filter monthly, so replace it sooner if it looks dirty, especially with pets, smoke or remodeling.
Is MERV 13 safe for my system?
EPA says most furnaces and HVAC systems can accommodate a MERV 13 filter without equipment problems if it is replaced frequently, but higher-MERV filters do tend to restrict airflow. A deep 5-inch filter has more media area than a thin one at the same rating. If you notice weak airflow or are unsure, ask an HVAC technician.
My filter says MPR or FPR, not MERV. What do I buy?
MPR (3M/Filtrete) and FPR (Home Depot) are proprietary scales, and EPA notes MERV is the national consensus standard, so conversions are approximate. Filterbuy maps roughly MPR 600 or FPR 5 to MERV 8, MPR 1000–1200 or FPR 7 to MERV 11, and MPR 1500–1900 or FPR 10 to MERV 13.
Which way does the arrow go?
Per ENERGY STAR, the airflow arrow on the filter frame should point toward the furnace or blower unit.
Sources
- Filterbuy — 16x25x5 air filters (three actual sizes, cabinet part numbers, service life)
- Filterbuy — Air filter sizes chart (nominal vs actual)
- Aerostar — Air filter sizes: nominal vs actual
- US EPA — What is a MERV rating?
- US EPA — Guide to Air Cleaners in the Home
- US EPA Indoor airPLUS — Filtration technical bulletin
- ENERGY STAR — How to keep your HVAC system working efficiently
- ENERGY STAR — Certified Homes maintenance guide