Nominal vs Actual Air Filter Size Chart
Nominal size is the rounded label used to identify a filter. Actual size is what a ruler measures. They are not always the same, and different manufacturers may use different actual dimensions for the same nominal label.
Plusco standard sizes
Plusco standard filters run half an inch under nominal in each dimension. A nominal 20 x 25 x 1 filter measures 19.5 x 24.5 x 0.5 inches. The width and height chart below covers all 24 sizes in our calculator. Click a size for prices across 1-, 2- and 4-inch depths.
| Nominal width x height (in.) | Plusco actual width x height (in.) |
|---|---|
| 10 x 20 | 9.5 x 19.5 |
| 10 x 24 | 9.5 x 23.5 |
| 10 x 25 | 9.5 x 24.5 |
| 12 x 12 | 11.5 x 11.5 |
| 12 x 20 | 11.5 x 19.5 |
| 12 x 24 | 11.5 x 23.5 |
| 12 x 25 | 11.5 x 24.5 |
| 14 x 20 | 13.5 x 19.5 |
| 14 x 24 | 13.5 x 23.5 |
| 14 x 25 | 13.5 x 24.5 |
| 16 x 20 | 15.5 x 19.5 |
| 16 x 24 | 15.5 x 23.5 |
| 16 x 25 | 15.5 x 24.5 |
| 18 x 20 | 17.5 x 19.5 |
| 18 x 24 | 17.5 x 23.5 |
| 18 x 25 | 17.5 x 24.5 |
| 20 x 20 | 19.5 x 19.5 |
| 20 x 24 | 19.5 x 23.5 |
| 20 x 25 | 19.5 x 24.5 |
| 20 x 30 | 19.5 x 29.5 |
| 24 x 24 | 23.5 x 23.5 |
| 24 x 30 | 23.5 x 29.5 |
| 25 x 25 | 24.5 x 24.5 |
| 30 x 30 | 29.5 x 29.5 |
Depth matters too
| Nominal depth (in.) | Plusco actual depth (in.) |
|---|---|
| 1 | 0.5 |
| 2 | 1.5 |
| 4 | 3.5 |
Do not order a deeper filter unless the slot accepts it. These measurements describe Plusco standard filters, not every brand's filters.
How to measure
Turn the system off before removing the old filter. Note the printed size, then measure the filter's width, height and depth with a ruler or tape measure. Record the actual measurements without rounding. If the old filter is damaged or missing, ask your HVAC technician to confirm the slot's requirements.
Ordering an exact custom size
Custom filters are cut to the measurements you specify. Unlike standard nominal sizes, we do not subtract half an inch from an exact custom order. Enter the dimensions in the custom-size calculator and check each one before adding the order to your cart.
Price a standard or custom filter. For larger sizes, multiple sizes or a bulk order, request a quote or call (561) 241-9666.