Three tools, one page, nothing to install. Convert whatever rating number is printed on your filter into every other system’s equivalent, find the nearest stocked size for a slot you measured yourself, and see what your filter actually costs per year, not just per purchase.
Rating Normalizer
Enter a MERV number, a Home Depot FPR number, or a Filtrete MPR number and get the other two, plus what that tier actually captures.
Size Helper
Measure your filter slot’s width and height, pick a depth, and get the nearest commonly stocked nominal size instead of guessing.
Cost-Per-Year Calculator
Pick a filter type or enter your own price and replacement interval to see the real annual cost, side by side with every other type.
How to use these
Rating normalizer: look at the box your current filter came in. If it says a plain number like 8 or 13, that’s MERV. If it says “FPR” and a number 4-10, that’s Home Depot’s scale. If it says “MPR” and a number in the hundreds, that’s Filtrete’s scale. Pick the matching option and enter the number. Full background on why three scales exist: MERV, FPR, and Every Filtrete Number Explained.
Size helper: measure the actual filter slot opening, not an old filter (it may already be the wrong size). Width and height to the nearest 1/4 inch is close enough. Full sizing walkthrough: HVAC Air Filter Sizes.
Cost calculator: the dropdown fills in typical price and interval for each filter type; edit either field to match your actual filter and household. Full type-by-type comparison: HVAC Air Filters: Sizes, MERV Ratings, and How Often to Replace Them.
Ready to buy? Real Amazon, Home Depot, and Lowe’s links for the sizes and MERV tiers these tools cover. Full list: MERV, FPR, and Every Filtrete Number Explained.
Frequently Asked Questions
Q: Are these calculators saving my data anywhere?
A: No. Everything runs in your browser; nothing you enter is sent anywhere or stored.
Q: Why doesn’t the size helper account for filter depth in the size match?
A: Depth (1, 2, 4, or 5 inch) is a separate choice from width and height because it depends on your system’s filter cabinet, not the slot opening measurement. Pick your depth from your current filter or your HVAC manual.
Q: The rating normalizer says “no exact match.” What does that mean?
A: Not every MERV value has a direct Filtrete or FPR product at that exact tier. The tool shows the closest available tier instead. See the full cross-reference for the complete table.
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Related: HVAC Air Filters: Sizes, MERV Ratings, and How Often to Replace Them · MERV, FPR, and Every Filtrete Number Explained · HVAC Air Filter Sizes · Best MERV Rating for Your Home · What Filter Does My Furnace Actually Need?
Sources & verification
✓ Verified against a manufacturer or standards source
- MERV/FPR/Filtrete MPR conversions used in the normalizer below are sourced from 3M’s own published chart — 3M Filtrete, ‘MPR vs MERV,’ https://multimedia.3m.com/mws/media/1740587O/filtrete-merv-vs-mpr.pdf
- Default cost-per-year figures use the price and replacement-interval ranges from our filter type guide — see HVAC Air Filters: Sizes, MERV Ratings, and How Often to Replace Them
⚠ Provisional — industry-average estimate, not a direct manufacturer/spec citation
- The size helper rounds up to the nearest commonly stocked nominal size; unusual or older HVAC systems may use a size outside this common list and need a specialty or cut-to-fit retailer
