Visibility Minimums Calculator

Work out visibility minimums instantly with clear inputs, formula shown and shareable results.

About Visibility Minimums Calculator

The visibility needed to complete an approach is driven by geometry: at decision height the aircraft is height / tan(path angle) from the touchdown zone, and the crew must see the required visual references over that distance plus a margin. Published minima always take precedence over this estimate.

Formula

Visibility geometry

slant distance = DH (m) / tan(path angle); required visibility approx 1.15 x that distance, floor 550 m

Worked example

With the default values below, Visibility Minimums Calculator returns Visibility required of 1,672. Change any input above and every figure here is recalculated in your browser.

Inputs used

Decision height or MDA above touchdown: 250 ft
Glide path angle: 3 °
Reported visibility: 1,200 m

Results

Visibility required: 1,672 m
Distance from touchdown at minimums: 1,454 m
Margin over the requirement: -472 m
Assessment: Below the estimated requirement

Step by step

1Values used
2Visibility geometry
3Visibility required= 1,672 m
4Distance from touchdown at minimums= 1,454 m
5Margin over the requirement= -472 m
6Assessment= Below the estimated requirement

Assumptions and limits

The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to whole numbers, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
Aviation results are planning estimates only. Always verify take-off, landing, fuel, weight and balance figures against the certified Aircraft Flight Manual, current performance charts and applicable aviation regulations before flight.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Aviation results are planning estimates only. Always verify take-off, landing, fuel, weight and balance figures against the certified Aircraft Flight Manual, current performance charts and applicable aviation regulations before flight.

Frequently Asked Questions

Is this a substitute for published minima?

No. Approach charts state the required RVR or visibility for each aircraft category and lighting configuration, and those values are the legal ones.

Why does approach lighting reduce minima?

Lights extend the visual segment before the runway, so the crew acquires references sooner and a lower RVR becomes acceptable.