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E6B Calc

How to read a METAR and TAF report, group by group

Read a METAR left to right: station, time, wind, visibility, weather, clouds, temperature over dew point, altimeter, remarks. The groups look dense at first, but reading one gets fast once they stop looking like noise. A TAF reuses the same codes for a forecast period and adds change groups — FM, BECMG, TEMPO, PROB. E6B Calc's METAR & TAF Decoder turns a pasted report into plain language offline, 3 free decodes before E6B Pro kicks in.

3 min read · Updated 2026-09-11

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A sample METAR, decoded

Made up for practice, this one, not a real observation: METAR KDEN 241753Z 20012G22KT 10SM FEW080 SCT200 31/04 A3012 RMK AO2 SLP101 T03060044

Each group of the sample METAR
GroupMeaning
KDENStation identifier (ICAO code)
241753ZDay 24 of the month, 1753 Zulu
20012G22KTWind from 200° true at 12 kt, gusting 22 kt
10SMVisibility 10 statute miles (outside the US, 4 digits in metres, or CAVOK)
FEW080 SCT200Few clouds at 8,000 ft and scattered at 20,000 ft above ground: no ceiling
31/04Temperature 31 °C, dew point 4 °C
A3012Altimeter setting 30.12 inHg (Q groups, such as Q1013, are hPa)
RMK AO2Remarks: automated station with a precipitation sensor
SLP101Sea-level pressure 1010.1 hPa
T03060044Exact temperature 30.6 °C and dew point 4.4 °C

A ceiling is the lowest broken (BKN) or overcast (OVC) layer, or vertical visibility (VV) — not FEW, not SCT, no matter how it looks out the window. Weather codes stack intensity and type: -RA light rain, +TSRA heavy thunderstorm with rain, BR mist, FG fog. BR and FG are easy to mix up; the decoder doesn't.

Flight categories

FAA categories take the worse of ceiling and visibility: VFR above 3,000 ft and 5 SM, MVFR 1,000–3,000 ft or 3–5 SM, IFR 500 ft to under 1,000 ft or 1 to under 3 SM, LIFR under 500 ft or under 1 SM. The sample above is VFR, comfortably.

How to read a TAF

A TAF opens with station, issue time and a validity period like 2418/2524 — 24th at 1800Z to the 25th at 2400Z — then a base forecast in the same METAR codes. The change groups after it are where most of the useful information actually lives:

  • FM: from this time on, a new set of conditions replaces the old one.
  • BECMG: a gradual change over the period given.
  • TEMPO: temporary fluctuations lasting less than an hour at a time, in total less than half the period.
  • PROB30 or PROB40: a 30 % or 40 % chance of the conditions that follow.

Decode a report in E6B Calc

  1. Copy the METAR or TAF from your briefing source.
  2. On E6B, open METAR & TAF Decoder under Weather and paste it into the box, or type it.
  3. Read the cards: Wind, Visibility, Weather, Sky, Ceiling, Flight category, temperature, dew point and Altimeter setting in your chosen unit. A TAF gets one card per change group.
  4. Tap Full decode for a plain-English line-by-line reading.
  5. For a METAR, tap Use this report, add field elevation, runway heading and magnetic variation, and get pressure altitude, density altitude, cloud base and runway crosswind.

The sample in numbers

Use this report: field elevation 5,434 ft, runway 170° magnetic, variation 8 °E
ResultValue
Pressure altitude5,250 ft
Density altitude8,170 ft
Cloud base AGL10,500 ft
Crosswind8 kt from the right
Head/tailwind20 kt headwind

Note it uses the 22 kt gust for the components, not the 12 kt steady wind, and the true wind of 200° becomes 192° magnetic before it ever gets compared to the runway heading. Temperature, meanwhile, comes from the sharper T-group rather than the rounded 31/04 up front.

What the decoder does not do

  • It never downloads reports: you paste them, so it works without signal.
  • The Full decode text is in English only.
  • Flight categories follow the US FAA thresholds.
  • If a report has a group it does not recognise, it shows Could not decode this report and names the group instead of showing a half-decoded result. A failed decode does not use a free visit.
  • It is hidden while Exam mode is on.

Questions and answers

Is the METAR decoder free?
You get 3 free visits that decode a report; a report that fails to decode is not counted. After that, unlimited decoding is part of the one-time E6B Pro purchase.
What does AO2 mean in a METAR?
It marks an automated station with a precipitation discriminator, which can tell rain from snow. AO1 stations cannot.
Are METAR winds true or magnetic?
True. Tower and ATIS winds are magnetic. That is why the decoder asks for magnetic variation before it works out runway crosswind.
Does it work with reports outside the US?
Yes, it reads metre visibility, CAVOK and hPa (Q) altimeter groups, and shows the altimeter in the unit you choose. Flight categories still use the FAA thresholds.

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