The Humidifier Output Index
"Covers up to X sq ft" is a marketing claim built on unstated assumptions about ceiling height, room sealing, climate, and target humidity. This dataset normalizes the spec that's actually physical and comparable: output, in both GPD and mL/hr, alongside tank capacity, the runtime that output implies, and the room volume the manufacturer's own coverage claim would require at a stated 8-foot ceiling assumption.
The one thing to know: A humidifier's 'covers up to X sq ft' claim silently assumes a specific ceiling height, a sealed room with no air exchange, a specific outdoor climate, and a specific target relative humidity — none of which the box tells you. Two rooms of the identical square footage can need completely different amounts of moisture depending on their volume (an 8 ft vs 10 ft ceiling is a 25% difference in air to humidify), their leakiness, and how dry the incoming outdoor air is. The physically meaningful spec is the humidifier's OUTPUT — gallons per day (GPD) or milliliters per hour (mL/hr) — not the sq ft claim built on top of it.
License & how to cite
License: CC BY 4.0 — free to use with attribution.
How to cite: Humidifier Decoded, "Humidifier Output Index," version 1.0, July 30, 2026, https://humidifier-decoded.pages.dev/humidifier-output-index/.
The dataset
| Model | Type | Filter? | Output (GPD) | Output (mL/hr) | Mfr. claimed sq ft | Derived room volume (ft³, 8 ft ceiling) | Tank (gal / L) | Runtime at max output (hrs) | Source class |
|---|---|---|---|---|---|---|---|---|---|
| Levoit LV600S | Ultrasonic | No | 3.17 | 500 | 753 | 6,024 | 1.59 / 6.0 | 12 | manufacturer spec |
| Levoit Dual 150 | Ultrasonic | No | 1.00 | 157 | 290 | 2,320 | 0.79 / 3.0 | 19.1 | manufacturer spec |
| Levoit Superior 6000S | Evaporative | Yes (wicking) | not published | not published | 3,000 | 24,000 | 6.0 / 22.71 | not calculable | manufacturer spec (partial) |
| Pure Enrichment MistAire | Ultrasonic | No | 0.95 | 150 | 250 | 2,000 | 0.40 / 1.5 | 10.0 | manufacturer spec |
| Pure Enrichment MistAire XL | Ultrasonic | No | not published | not published | 500 | 4,000 | 1.0 / 3.79 | not calculable | manufacturer spec (partial) |
| Honeywell HCM350 | Evaporative | Yes (wicking + UV) | 2.0 | 315.5 | 500-800 | 4,000-6,400 | 1.1 / 4.16 | 13.2 | manufacturer spec |
| Vicks V745A | Warm mist | No (filter-free) | 3.0 (derived) | 473.2 (derived) | 250-400 | 2,000-3,200 | 1.0 / 3.79 | 8.0 | derived calculation |
| AIRCARE Valiant | Evaporative (whole-house console) | Yes (wicking) | 12.81 | 2,021.4 | 4,000 | 32,000 | 5.0 / 18.93 | 9.37 | manufacturer spec |
| AIRCARE Alliance H12600 | Evaporative (whole-house console) | Yes (wicking) | 12.0 | 1,892.7 | 3,700 | 29,600 | 5.4 / 20.44 | 10.8 | manufacturer spec |
Room volume = manufacturer's claimed sq ft × 8 ft, an explicitly assumed standard ceiling height (the manufacturer does not state a ceiling height, so this figure is derived, not manufacturer-published). Runtime at max output = tank capacity ÷ max output rate — usually shorter than the manufacturer's advertised "up to N hours" runtime, which is typically measured at the lowest mist/fan setting.
Why room volume, not just square footage
A 300 sq ft room with an 8-foot ceiling holds 2,400 cubic feet of air; the same 300 sq ft room with a 10-foot ceiling holds 3,000 cubic feet — 25% more air to humidify, from an identical floor-plan number on the box. No humidifier manufacturer we reviewed states a ceiling-height assumption behind its sq ft claim. We use 8 feet as a standard assumption and label the resulting volume figure as derived so it is never confused with a manufacturer specification.
Caveats — read before citing a figure
- "Not published" means we could not verify a figure, not that the humidifier has no output — it means the manufacturer's spec sheet and major retail listings did not state a GPD or mL/hr number.
- "Derived" means we calculated it, typically tank capacity ÷ a published runtime figure. Treat derived numbers as estimates, not manufacturer ratings.
- Runtime at max output is a worst-case-for-refills number, not a recommendation to always run at max — most owners run these units at lower settings for longer, quieter operation.
- Whole-house console units (AIRCARE Valiant, Alliance) are reservoir-fed, designed for continuous refill, not tank-to-empty operation — their "runtime at max output" figure is a theoretical ceiling, not typical usage.
- This dataset is equipment-spec reference, not a health or safety verdict for any room or occupant.
Methodology & versioning
Version 1.0 — published July 30, 2026. Output, tank, and coverage figures are drawn from manufacturer product pages and specification sheets, cross-checked against major retailer listings (Sylvane, Home Depot, Walmart, Amazon) where the manufacturer page lacked a figure. GPD and mL/hr are interconverted using 1 gallon = 3,785.41 mL. We do not test humidifiers ourselves; this is a specification-facts reference. Corrections: if a manufacturer updates a spec or we find an error, this page and its CSVs are updated in place and the version/date bumped — see How We Evaluate for our full editorial policy.
Machine-readable download: full table at /humidifier-output-index.csv (version-pinned copy: /humidifier-output-index-v1.0.csv), condensed digest in /llms-full.txt.
This page is equipment specification reference, not a health or safety determination for any room or occupant.
Frequently Asked Questions
A normalized reference dataset of popular current humidifiers, listing output in both GPD and mL/hr, the manufacturer's claimed sq ft coverage next to the room volume that output actually supports (at a stated 8-foot ceiling assumption), tank capacity, the runtime that output implies, humidifier type, and whether a replaceable filter is required.
Square footage ignores ceiling height, and an 8-foot vs. 10-foot ceiling is a 25% difference in the actual volume of air being humidified. We multiply the manufacturer's claimed sq ft by an explicitly stated 8-foot ceiling assumption to derive a cubic-foot volume figure — always labeled as derived, since the manufacturer did not state a ceiling height themselves.
Several manufacturers and retail listings advertise a tank size and a sq ft coverage claim but do not publish an actual GPD or mL/hr output rate anywhere we could verify. Rather than guess, we mark these as not published — it is itself useful information about a gap in the spec sheet.
It means we calculated that figure ourselves — usually tank capacity divided by a published runtime — rather than the manufacturer stating an output rate directly. Derived figures are estimates, not manufacturer specifications, and are labeled as such throughout.
Because advertised runtime figures (e.g., 'up to 50 hours') are almost always measured at the lowest mist or fan setting, while our runtime figure divides tank capacity by the MAXIMUM output rate used elsewhere on the same spec sheet. Both numbers are true; they're measured at different settings.