Aviation Weather

Flight Category Estimator

Flight categories sort reported weather into four groups by ceiling and visibility: VFR, MVFR (marginal VFR), IFR, and LIFR (low IFR). MVFR means a ceiling of 1,000 to 3,000 feet or visibility of 3 to 5 statute miles. Whichever of the two is lower sets the category. Enter a ceiling and visibility below to see which category they fall in.

Educational lookup, not a weather briefing. What it leaves out

Flight category thresholds by ceiling and visibility
Category	Ceiling (ft AGL)	Visibility
VFRVisual Flight Rules	Above 3,000 ft	More than 5 SM
MVFRMarginal VFR	1,000 to 3,000 ft	3 to 5 SM
IFRInstrument Flight Rules	500 to below 1,000 ft	1 to less than 3 SM
LIFRLow IFR	Below 500 ft	Less than 1 SM

The ceiling is the lowest broken (BKN) or overcast (OVC) layer. If either value falls in a lower category, that lower category is the one reported.

Ceiling (ft AGL)No ceiling (clear, few, or scattered)

Visibility (SM)

Prevailing visibility in statute miles

MVFR

Marginal Visual Flight Rules

Ceiling and visibility both point to MVFR.

Ceiling 1,200 ftMVFR

Visibility 4 SMMVFR

Ceiling 1,000-3,000 ft AGL and/or visibility 3-5 SM. Conditions are close to the boundary between visual and instrument categories, and can move across it quickly.

How Ceiling and Visibility Combine

Find the ceiling on the left and the visibility across the top. The reported category is always the lower of the two.

Flight category for each combination of ceiling band and visibility band
Ceiling \ Visibility	More than 5 SM	3 to 5 SM	1 to less than 3 SM	Less than 1 SM
Above 3,000 ft	VFR	MVFR	IFR	LIFR
1,000 to 3,000 ft	MVFR	MVFR	IFR	LIFR
500 to below 1,000 ft	IFR	IFR	IFR	LIFR
Below 500 ft	LIFR	LIFR	LIFR	LIFR

Understanding Flight Rules

What is Ceiling?

Ceiling is the height of the lowest cloud layer reported as broken (BKN) or overcast (OVC). Few (FEW) and scattered (SCT) clouds do not constitute a ceiling. If no BKN or OVC layer exists, the ceiling is considered unlimited.

Prevailing Visibility

Visibility is the greatest horizontal distance objects can be seen, reported in statute miles at airports. It can be reduced by fog, haze, rain, snow, or other obstructions. METAR reports include prevailing visibility after the wind group.

The Limiting Factor

The reported category is set by the more restrictive of ceiling or visibility. If the ceiling indicates VFR but visibility indicates IFR, the reported category is IFR. Both values always have to be read together.

Common Weather Scenarios

VFR

Clear skies, 10+ SM visibility

Ideal flying conditions. All pilot certificates. Standard VFR cloud clearance and visibility requirements apply.

MVFR

Hazy morning, 2,500 ft overcast, 4 SM visibility

Common in early morning or after frontal passage. VFR flight still legal but requires extra vigilance. Conditions may improve or deteriorate rapidly.

IFR

Low stratus, 800 ft overcast, 2 SM in mist

Requires instrument rating, IFR flight plan, and ATC clearance. Common during fog, low stratus, or steady precipitation events.

LIFR

Dense fog, 200 ft overcast, 1/4 SM visibility

Extremely challenging conditions. Many instrument approaches have higher minimums than LIFR conditions. Diversions are common. Consider waiting for improvement.

Not for flight planning

This is an educational lookup of a weather reporting convention. It is not a briefing, it does not make a go/no-go determination, and it cannot tell you what a flight is permitted to do. Obtain an official FAA-approved weather briefing, current METARs and TAFs, NOTAMs, and the applicable regulations, approach minimums, and aircraft limitations before any flight.

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Frequently Asked Questions

What is the difference between VFR and IFR?

As weather reporting categories, VFR requires visibility greater than 5 statute miles and a ceiling above 3,000 feet AGL, or no ceiling. IFR applies when the lower category from ceiling and visibility falls between 500 and below 1,000 feet AGL, or between 1 and below 3 statute miles. VFR and IFR also name operating rules. A weather category alone does not determine which rules a flight may legally use.

What does MVFR mean?

MVFR means Marginal Visual Flight Rules. The reporting thresholds are a ceiling of 1,000 to 3,000 feet AGL or visibility of 3 to 5 statute miles. If either measurement meets IFR or LIFR criteria, that lower category controls. Flight legality depends on the applicable operating rules and airspace minimums.

What does LIFR mean in aviation?

LIFR means Low Instrument Flight Rules. A ceiling below 500 feet AGL or visibility below 1 statute mile places conditions in this reporting category. It does not establish whether a particular instrument approach can be flown; published minimums and other operational requirements must be checked separately.

Does the ceiling or the visibility set the flight category?

Whichever is lower. Each value is placed in its own category, and the more restrictive of the two is reported. A 4,000-foot ceiling with 2 statute miles of visibility is IFR, because the visibility alone falls in the IFR range even though the ceiling is VFR.

Can I fly VFR in MVFR conditions?

MVFR is a reporting category, not an operating rule, so VFR flight can be legal in MVFR conditions where the cloud clearance and visibility minimums for the airspace are met. MVFR does mean reduced margins and conditions that can drop into IFR, so a plan for diverting matters more than usual.

Where do flight categories appear on METARs?

Flight categories are not encoded in a METAR. They are derived from its ceiling (the lowest BKN or OVC layer, or vertical visibility) and its prevailing visibility in statute miles. Aviation weather displays, including the Aviation Weather Center, color-code stations by category: green for VFR, blue for MVFR, red for IFR, and magenta for LIFR.

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