HVAC filter guide
16 × 20 × 1 air filters
How to confirm this nominal size, what the dimensions mean, and a manually verified product option.
Read the guide →Homeowner guides
Useful answers for the details your house makes you remember.
HomeOS guides focus on practical home questions: what a number means, what to check before you buy, and when it is better not to guess.
HVAC filter guide
16 × 25 × 1 air filters
How to confirm this nominal size, what the dimensions mean, and a manually verified product option.
Read the guide →HVAC filter guide
20 × 20 × 1 air filters
How to confirm this nominal size, what the dimensions mean, and a manually verified product option.
Read the guide →HVAC filter guide
20 × 25 × 1 air filters
How to confirm this nominal size, what the dimensions mean, and a manually verified product option.
Read the guide →More homeowner guides
Practical answers for the things that are easy to forget until they matter.
HVAC basics
How to find your HVAC filter size
Where to look, what the numbers mean, and what to do when the size is missing.
Read the guide →HVAC basics
MERV 8 vs. MERV 11 vs. MERV 13
What the ratings mean and why higher filtration is not automatically right for every system.
Read the guide →Home maintenance
How often should you change an HVAC filter?
Why replacement timing depends on the filter, equipment, season, and home.
Read the guide →HVAC basics
Which way should the filter arrow point?
How to identify airflow direction at a return grille, furnace, or air handler.
Read the guide →HVAC basics
What if an HVAC filter is too small or too big?
Why near matches can leave gaps, distort the filter, or simply fail to fit.
Read the guide →Home maintenance
A practical new homeowner maintenance checklist
The first home facts and maintenance items worth learning and recording.
Read the guide →Not sure which filter size you have?
Start with the filter already installed. The printed nominal size is usually the safest replacement reference.
Read the complete HVAC filter-size guide