HVAC Filter Size Finder

Not sure what filter your HVAC system needs? Enter your filter dimensions or pick from common sizes to get personalized recommendations on filter type, MERV rating, price range, and how often to replace it.

How It Works

Enter your filter dimensions (length x width x depth) or select from the most common residential sizes. The tool recommends appropriate filter types and MERV ratings based on your size, explains what each MERV level filters out, provides cost estimates per filter, and tells you how often to replace it based on Central Texas conditions -- where extended cooling seasons, heavy pollen, and construction dust mean filters need more frequent changes than national averages suggest.

Filter sizes are listed as nominal (rounded) dimensions rather than actual measurements. For example, a "20x25x1" filter actually measures approximately 19.5 x 24.5 x 0.75 inches. When measuring for a replacement, always round up to the nearest standard size. If no size is printed on your current filter, remove it and measure the length, width, and depth with a tape measure.

Most Common Residential Filter Sizes

16 x 20 x 1 16 x 25 x 1 20 x 20 x 1 20 x 25 x 1 20 x 25 x 4 20 x 30 x 1 24 x 24 x 1 25 x 25 x 1

MERV Rating Quick Guide

  • MERV 1-4: Basic fiberglass -- captures large dust and lint only
  • MERV 5-8: Standard pleated -- good for most homes, captures dust mites and mold spores
  • MERV 8-11: Better pleated -- recommended balance of filtration and airflow for most systems
  • MERV 11-13: High-efficiency -- captures fine particles, pollen, pet dander; ideal for allergy sufferers
  • MERV 14+: Hospital-grade -- not recommended unless your system is specifically designed for it

How to Measure Your Filter

  1. Turn off your HVAC system
  2. Locate the filter (usually at the return air vent or inside the air handler)
  3. Remove the existing filter and check for a size printed on the frame
  4. If no size is printed, measure width x height x depth in inches
  5. Actual sizes are usually 1/4" to 1/2" smaller than the nominal (listed) size

Common Filter Sizes and Recommendations

20x25x1 Standard

Size
20" x 25" x 1"
Type
Pleated
MERV Rating
8–11
Replace Every
60–90 days
Cost
$8–$15 each

The most common residential filter size. MERV 8-11 balances good filtration with minimal airflow restriction.

20x25x4 Deep Pleated

Size
20" x 25" x 4"
Type
Deep pleated media
MERV Rating
11–13
Replace Every
6–12 months
Cost
$25–$45 each

Deep pleated filters last much longer and provide better filtration. Ideal for Texas homes with pets or allergy concerns.

16x20x1 Allergy

Size
16" x 20" x 1"
Type
Electrostatic pleated
MERV Rating
11–13
Replace Every
60 days
Cost
$15–$25 each

Higher MERV ratings capture pollen, mold spores, and pet dander — critical during Central Texas cedar season (Dec-Feb).

Why Your HVAC Filter Matters

Your air filter is the first line of defense for both your indoor air quality and your HVAC system's health. A clean, properly sized filter traps dust, pollen, pet dander, and other airborne particles before they circulate through your home or clog your system's evaporator coil. In Central Texas, where allergens like cedar pollen (December-February) and ragweed (fall) are exceptionally high, filter selection is especially important.

Choosing the Right MERV Rating

MERV (Minimum Efficiency Reporting Value) rates a filter's particle-capturing ability on a scale of 1 to 20. For most Texas homes, a MERV 8-13 pleated filter provides the best balance of air quality and system performance. While higher MERV ratings capture more particles, they also restrict airflow. Using a MERV 14+ filter on a system not designed for it can reduce airflow, cause the evaporator coil to freeze, and increase energy consumption by 5-10%. Always check your system's specifications before upgrading filter efficiency.

How Often to Change Your Filter in Texas

Standard 1-inch pleated filters should be changed every 60-90 days under normal conditions. However, in Central Texas you may need to replace them more frequently due to:

  • Extended cooling seasons (8-9 months of AC use) meaning more air passes through the filter
  • Construction dust in rapidly growing areas like Killeen and Temple
  • Pet hair and dander — households with pets should change every 30-60 days
  • Allergy sufferers benefit from monthly changes during peak pollen seasons

Measuring Your Filter Correctly

Filter sizes are listed as nominal (rounded) dimensions, not actual measurements. For example, a "20x25x1" filter actually measures approximately 19.5" x 24.5" x 0.75". When measuring for a replacement, round up to the nearest standard size. If your filter slot is an unusual size, custom-cut filters are available from specialty suppliers.

Need help with filter selection or maintenance? Contact Texas Temp Masters — our maintenance plans include regular filter changes and system inspections.

Related Resources

Related Tools

Helpful Articles

Need Emergency HVAC Service?

Don't wait when your heating or cooling system fails. Our licensed technicians provide same-day emergency service throughout Central Texas with guaranteed satisfaction.