YOUR EQUIPMENT FIRST
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Compare actual filter dimensions
Example input and result
Actual15.5 ×19.5 ×0.75in, with equipment requirements confirmed, matches the nominal16 ×20 ×1 reference. This is dimensional agreement only; it does not confirm clearance, airflow, seals or installation fit.
Illustrative values only; nothing is entered into the form automatically.
Use the actual dimensions required by your equipment. The size printed on a filter pack may be nominal. This tool compares three Nordic Pure MERV 8 six-pack size examples; it does not confirm installation fit or recommend a filtration level.
Comparison result
Size examples
These are Nordic Pure MERV 8 six-pack dimensions checked on October 25, 2026. They are reference examples, not a live product-availability list. Nominal sizes are labels, not actual dimensions. There is no “closest fit” recommendation.
| Nominal label | Actual dimensions (in) |
|---|
A dimensional match compares the numbers entered. It cannot establish slot clearance, seals, airflow, measurement accuracy or overall system compatibility. If your manual and measurement disagree, pause and ask the equipment manufacturer or an HVAC professional.
Review the current air-filter category · Read the filter-fit guide
Plan a maintenance date
Use the interval stated for your exact equipment and task. This planner adds the number of days you enter; it does not recommend how often to replace a filter or service equipment.
Winter planning example
Suppose your own equipment instructions specify a fixed 30-day interval for a particular maintenance task, completed on October 1, 2026. Enter October 1 and 30 days; the planner returns October 31, 2026.
The 30 days are an arithmetic example, not a recommended filter-change interval. Use your exact instructions. If the task is condition-based, expressed in months or requires an inspection, do not replace it with an invented day count. No reminder is scheduled and no entries are saved or transmitted.
Enter your completed maintenance date and the interval specified for your equipment.
Review filter requirements before planning a filter task. For other tasks, use your exact equipment instructions.
No reminder is scheduled and your entries are not saved or transmitted. Follow the manual and actual conditions; a calculated date does not replace inspection or qualified service.
Convert length units
Example input and result
12in →304.8mm. This converts length; it does not establish equipment compatibility.
Illustrative values only; nothing is entered into the form automatically.
Enter a nonnegative decimal length. This converts units only; it does not turn a nominal filter label into an actual size. Use a decimal point; fractions and scientific notation are not accepted. Changing an input unit or currency clears this tool's numbers.
Enter your values, then calculate.
Convert temperature units
Example input and result
20°C →68°F. This converts a temperature, not a recommended thermostat setting or comfort/safety target.
Illustrative values only; nothing is entered into the form automatically.
Convert an absolute temperature, not a temperature difference. No thermostat setting or operating target is recommended. Values below absolute zero are not accepted. Use a decimal point; fractions and scientific notation are not accepted. Changing an input unit or currency clears this tool's numbers.
Enter your values, then calculate.
Calculate rectangular room area
Example input and result
12ft ×10ft →120ft². Rectangular floor geometry only; not heating or cooling capacity.
Illustrative values only; nothing is entered into the form automatically.
Enter positive length and width in the same unit. This is rectangular geometry only, not a cooling-capacity, BTU or equipment-sizing calculation. Split an irregular floor plan into measured rectangles separately. Use a decimal point; fractions and scientific notation are not accepted. Changing an input unit or currency clears this tool's numbers.
Enter your values, then calculate.
Calculate rectangular room volume
Example input and result
12ft ×10ft ×8ft →960ft³. Rectangular volume only; not a ventilation or equipment-sizing assessment.
Illustrative values only; nothing is entered into the form automatically.
Enter positive length, width and uniform height in the same unit. This simple box does not model a sloped or variable ceiling and does not size HVAC equipment. Use a decimal point; fractions and scientific notation are not accepted. Changing an input unit or currency clears this tool's numbers.
Enter your values, then calculate.
Convert airflow units
Example input and result
100CFM →169.90m³/h (rounded). This converts the supplied flow value; it does not measure airflow.
Illustrative values only; nothing is entered into the form automatically.
Convert a nonnegative volume-flow number under the same measurement conditions. This does not measure a fan, establish CADR, or convert between standard and actual air conditions. Use a decimal point; fractions and scientific notation are not accepted. Changing an input unit or currency clears this tool's numbers.
Enter your values, then calculate.
Calculate air changes per hour (ACH)
Example input and result
An independently measured80CFM and room volume960ft³ →5changes/hour. Arithmetic only, not a health or ventilation target. Recirculation is not outdoor air or clean-air delivery; do not add supply and exhaust.
Illustrative values only; nothing is entered into the form automatically.
Use an independently measured flow and a positive room volume. Result = flow per hour divided by volume. It is not a ventilation target, safety assessment or equipment-sizing recommendation. Recirculated fan flow is not outdoor-air ventilation or clean-air delivery; do not add supply and exhaust together. Use a decimal point; fractions and scientific notation are not accepted. Changing an input unit or currency clears this tool's numbers.
Enter your values, then calculate.
Estimate energy and cost from your inputs
Example input and result
Average100W ×8hours/day ×30days →24kWh. At an illustrative USD0.20/kWh, estimated cost is USD4.80. This is not a tariff, bill or savings guarantee; cycling, standby, taxes, fees and variable rates are not modelled.
Illustrative values only; nothing is entered into the form automatically.
Enter average active watts, 0–24 hours per day, 0–36500 whole days and your own currency-per-kWh price. No tariff is prefilled. Constant power is assumed; cycling, standby, taxes, fixed fees and variable tariffs are not modelled. This is not a bill or savings guarantee. Use a decimal point; fractions and scientific notation are not accepted. Changing an input unit or currency clears this tool's numbers.
Enter your values, then calculate.
Compare two filter-pack unit costs
Example input and result
PackA:USD48 for6filters →USD8/filter. PackB:USD30 for3 →USD10/filter. Example prices only; lower unit cost does not prove equal models, fit, quality or service life.
Illustrative values only; nothing is entered into the form automatically.
Enter both package totals in the same currency and whole filter counts from 1 to 1000000. Include shipping or tax in the totals if you want them included. Prices are entered by you, not fetched from Amazon. Unit price does not establish equal models, fit, quality, service life or the best purchase. Use a decimal point; fractions and scientific notation are not accepted. Changing an input unit or currency clears this tool's numbers.
Enter your values, then calculate.
Read the filter size guide · Choose tools by task
Formulas and limits
Unit conversions follow NIST conversion factors and the international foot (0.3048 m). Airflow rate divided by room volume follows the arithmetic in CDC/NIOSH ventilation guidance; no recommended ACH or health outcome is provided. Energy is watts × hours ÷ 1000 and cost is kWh × your entered price. See Virginia Tech appliance-energy guidance for why actual use can differ. Display rounding does not increase the precision of your measurements.
All calculations stay in this browser. No entries or results are saved, sent or used to select a product automatically.
Open the blank filter and maintenance notes card, then use your browser’s Print command.