{
  "slug": "dew-point-calculator",
  "title": "Dew Point Calculator",
  "heading": "Dew Point Calculator",
  "category": "other",
  "url": "https://www.revenuelab.fyi/toolbox/dew-point-calculator",
  "summary": "Compute dew point and comfort level from temperature and relative humidity.",
  "description": "Dew point is the temperature air must cool to for water vapor to condense, and unlike relative humidity it directly tells you how muggy the air actually feels regardless of temperature. A 60°F dew point feels sticky whether the air temp is 75°F or 95°F, which is why meteorologists prefer it over RH for describing outdoor comfort. This calculator uses the Magnus-Tetens approximation, accurate to within about 0.4°C across typical weather ranges. Dew point also predicts fog and frost formation: when overnight lows approach the dew point, expect fog, and if the dew point is at or below freezing, expect frost instead of dew.",
  "formula": "α = ln(RH/100) + (17.625×T)/(243.04+T); dew point = 243.04×α / (17.625−α), computed in °C then converted to °F.",
  "dateModified": "2026-09-30",
  "run_url": "https://www.revenuelab.fyi/api/public/calc?tool=dew-point-calculator",
  "inputs": [
    {
      "id": "temp",
      "label": "Air temperature",
      "kind": "number",
      "hint": null,
      "default": 82,
      "unit": "°F",
      "min": -20,
      "max": 130
    },
    {
      "id": "rh",
      "label": "Relative humidity",
      "kind": "number",
      "hint": null,
      "default": 65,
      "unit": "%",
      "min": 1,
      "max": 100
    }
  ],
  "outputs": [
    {
      "id": "dpF",
      "label": "Dew point",
      "format": "number",
      "hint": null,
      "primary": true
    },
    {
      "id": "dpC",
      "label": "Dew point (°C)",
      "format": "number",
      "hint": null,
      "primary": false
    },
    {
      "id": "comfort",
      "label": "Comfort level",
      "format": "raw",
      "hint": null,
      "primary": false
    }
  ],
  "worked_example": {
    "inputs": [
      "Air temperature: 82 °F",
      "Relative humidity: 65 %"
    ],
    "outputs": [
      "Dew point: 69.1",
      "Dew point (°C): 20.6",
      "Comfort level: Humid"
    ]
  },
  "how_to": {
    "title": "How to use this",
    "steps": [
      "Enter air temperature (°F).",
      "Enter relative humidity (%).",
      "Read your dew point on the right — it updates as you type.",
      "Hit Share to keep the scenario or send it to someone."
    ]
  },
  "scenarios": [
    {
      "name": "Conservative",
      "description": "Lower-end numbers — what if things land soft?",
      "values": {
        "temp": 49,
        "rh": 39
      }
    },
    {
      "name": "Typical",
      "description": "Defaults — the most common real-world setup.",
      "values": {
        "temp": 82,
        "rh": 65
      }
    },
    {
      "name": "Ambitious",
      "description": "Higher-end numbers — what if things really pop?",
      "values": {
        "temp": 130,
        "rh": 100
      }
    }
  ],
  "limitations": [
    "Estimates assume standard, average conditions — local rules, pricing, and materials vary.",
    "Results are rounded for readability; add a buffer before ordering, booking, or committing.",
    "Double-check anything with a real cost attached against a local quote."
  ],
  "faq": [
    {
      "q": "Why is dew point a better muggy-day indicator than humidity percentage?",
      "a": "Relative humidity is relative to the current temperature, so 50% RH at 60°F holds far less actual moisture than 50% RH at 95°F. Dew point measures absolute moisture content directly, so a 68°F dew point feels equally sticky whether it's 80°F or 100°F outside."
    },
    {
      "q": "What dew point predicts frost?",
      "a": "If the dew point is at or below 32°F and the surface cools to that temperature overnight, water vapor deposits directly as frost instead of condensing as dew, which is why forecasters watch dew point closely during shoulder-season nights."
    },
    {
      "q": "Can dew point ever be higher than air temperature?",
      "a": "No — dew point can equal air temperature (100% RH, saturated air, typically producing fog or rain) but can never exceed it, since that would mean condensation happens above the actual air temperature, which is physically impossible."
    },
    {
      "q": "What dew point is considered uncomfortable outdoors?",
      "a": "Most people start feeling sticky around 65°F, it's widely considered oppressive by 75°F, and dew points above 80°F (common in the Gulf Coast and Southeast Asia in summer) represent some of the most humid conditions found anywhere on Earth."
    }
  ],
  "related": [
    "https://www.revenuelab.fyi/toolbox/heat-index-calculator",
    "https://www.revenuelab.fyi/toolbox/relative-humidity-wet-bulb"
  ],
  "license": "CC-BY-4.0",
  "citation": "RevenueLab — Dew Point Calculator (https://www.revenuelab.fyi/toolbox/dew-point-calculator)"
}