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Canada Filter Sizes
Quick answer: Canadian furnace and air handler filters are sold in the same inch-based nominal sizes as in the United States, such as 16x25x1 or 20x25x4, even though metric is used elsewhere. Read the inch size from your old filter, round up measured sizes, and compare MERV ratings rather than store-brand scales. Availability differs by retailer more than by size.
Inches in a metric country
Canada adopted metric decades ago, but residential HVAC equipment and ductwork largely follow North American inch-based standards. Furnaces, air handlers, grilles and filters are designed and sold in inches. Some packaging shows a metric conversion in small print — for example "40.6 × 63.5 cm" for 16x25 — but shelves and online listings are organized by inch sizes. If you measured in centimetres, divide by 2.54 to convert to inches, then round up to the next whole inch.
Common sizes in Canadian homes
| Nominal (in) | Approx. metric face (cm) | Typical setting |
|---|---|---|
| 16x25x1 | 40.6 × 63.5 | Furnace slots in many basements |
| 16x20x1 | 40.6 × 50.8 | Smaller furnaces, condos |
| 20x25x1 | 50.8 × 63.5 | Large furnace slots and grilles |
| 16x25x4 / 16x25x5 | 40.6 × 63.5 | Media cabinets on newer furnaces |
| 20x25x4 / 20x25x5 | 50.8 × 63.5 | Media cabinets on larger systems |
| 14x25x1 | 35.6 × 63.5 | Narrow side slots on some furnaces |
Metric values are simple conversions of nominal inches, not actual sizes. See nominal vs actual.
Basement furnaces
Many Canadian homes have a gas furnace in the basement with a filter slot at the side or bottom of the return plenum, often a 16x25x1 or a media cabinet. Because winters are long and furnaces run many hours, filters can load faster than the calendar on the box suggests. Check monthly during the heating season.
Heat pumps and dual-fuel systems
Cold-climate heat pumps are increasingly common in Canada, sometimes paired with a gas furnace. They run long cycles year-round, moving a lot of air through the filter. The filter size is set by the furnace or air handler, but change intervals may need shortening. The schedule tool accounts for heavy runtime.
MERV vs brand scales
Canadian retailers often stock filters with their own rating scales alongside MERV. FPR and MPR scales are brand systems, not MERV. Look for the MERV number on the packaging to compare across brands. MERV is defined by ASHRAE Standard 52.2; the U.S. EPA summarizes it, and Health Canada publishes indoor air guidance for homeowners. See MERV explained.
Worked example
A homeowner in Ottawa measures an old filter at 39.4 × 62.2 cm. Dividing by 2.54 gives about 15.5 × 24.5 inches — the actual size of a 16x25. The slot is 1 inch deep, so they buy 16x25x1 MERV 8 pleated filters at a hypothetical $11 CAD each. During the November-to-March heating season they change every 60 days, and every 90 days the rest of the year, about five filters a year, roughly $55 CAD.
Illustrative note (2026-10-29): This example was written on 2026-10-29 for illustration. Measurements, prices and intervals are hypothetical; check current prices at your local retailer.
Where Canadians buy filters
Big-box hardware stores, home improvement chains, grocery and department stores, furnace dealers and online retailers all carry filters. Common 1-inch sizes are easy to find. Media filters for specific cabinets may be easier to buy from HVAC dealers or online. Cross-border online orders can add shipping and duties, so compare final prices.
Wildfire smoke seasons
Smoke from wildfires has affected many Canadian regions in recent summers. Public-health agencies have suggested higher-efficiency filtration where systems can handle it. If you plan to upgrade during smoke season, check that your system can tolerate higher MERV, change the filter more often while smoke persists, and follow your provincial or local public-health guidance. We make no health claims for any filter.
Humidity and winter
Furnace humidifiers are common in Canadian homes. A humidifier mounted on the return or supply can add moisture near the filter area; make sure filter frames stay dry and that the humidifier is maintained per its manual. A soggy filter frame can sag and leak.
French-language labels
Products sold in Canada carry bilingual packaging. "Filtre de fournaise" or "filtre à air" with "MERV" and the inch size is the same product category. Sizes are still written in inches (po).
Condos and rentals
Many Canadian condos use fan coils or heat pumps with small filters maintained by building staff. Check your condo rules or lease. See apartment filters.
Rebates and programs
Some provinces and utilities offer rebates for heat pumps or energy upgrades; filters themselves are rarely covered. Check your provincial program details directly; we do not track rebate eligibility.
Older homes and converted systems
Many older Canadian houses started with oil or gravity furnaces and were converted to forced-air gas over the decades. Return ducts in these homes were sometimes added in odd places, and filter slots may be non-standard sizes cut by an installer years ago. If your filter does not match a common size, look for a furnace label inside the blower door listing the filter size, or measure carefully and order a custom size. A filter that fits loosely in a site-cut slot leaks air; a technician can fit a proper filter rack or media cabinet during a furnace service.
Seasonal pattern for changes
In much of Canada, the furnace works hardest from November to March, and air conditioning or heat pump cooling runs in July and August. Spring and fall shoulder seasons are mild, with little runtime. That makes a seasonal pattern sensible: change at the start of the heating season, again mid-winter, at the start of cooling and once more in late summer, checking monthly in between. Homes that run the furnace fan continuously for ventilation or air circulation should lean toward more frequent changes.
HRVs and ERVs have their own filters
Many newer Canadian homes have a heat recovery or energy recovery ventilator. These units have their own filters, separate from the furnace filter, and usually need cleaning or replacement per the HRV manual.
Frequently asked questions
Are Canadian filter sizes different from U.S. sizes?
No. They are the same inch-based nominal sizes.
My filter is labelled in cm. What do I buy?
Convert to inches and match the inch size; look for the nominal size on the frame.
Do Canadian stores use MERV?
Most packages show MERV, often alongside brand scales.