Ensure a perfect fit—every time.
Before buying your next air filter, take a minute to measure correctly. A properly sized filter means better air quality, optimal system performance, and peace of mind.
🧭 Why Measuring Matters
Incorrect filter sizes can cause:
- 🛑 Air bypass and poor filtration
- ⚡ Reduced HVAC efficiency
- 💸 Higher energy bills
- 🔧 Increased system wear and tear
📌 Avoid frustration—measure first for the best fit.
📏 Nominal vs. Actual Size
| Term | Meaning |
| Nominal Size | The rounded, labeled size (e.g., 16x25x1) |
| Actual Size | The true dimensions (usually 0.25″–0.5″ smaller) |
📝 Example:
A filter labeled 16x25x1 may actually measure 15.5″ x 24.5″ x 0.75″
✅ Always confirm actual measurements before purchasing, especially for tight or custom slots.
📐 How to Measure an Air Filter
You can measure:
- An existing filter (recommended)
- The filter slot or housing
Option 1: Measure the Old Filter
- Remove it from the return vent or slot.
- Measure length x width x depth with a tape measure.
- Round up to the nearest inch for the nominal size.
- Double-check printed dimensions on the frame if visible.
Option 2: Measure the Slot
- Measure the internal dimensions of the slot or grille.
- Subtract 0.25″–0.5″ to account for filter clearance.
- Choose a filter with actual dimensions slightly smaller than the opening.
📦 Ordering Your Filter
✅ Know your size? Shop By Size
🛠️ Need a custom fit? Order a Custom Filter
Nordic Pure offers standard and custom filters made to your exact specifications.
💡 Pro Tips for Accurate Measuring
- ✍️ Write down your exact size for future reorders.
- 🔄 Switching brands? Always verify actual dimensions.
- 🧠 When in doubt-measure twice! What is Nominal vs. Actual Size? Learn More!
