Atmospheric Observation

Cloud Cover & Oktas Log

Convert approximate sky coverage and eighths into an editable cloud-amount log.

Use this tool

Preparing interactive controls…

Input conventionVisible sky covered (%)Sky obscured; amount cannot be estimated

Inverse percentages are nominal eighth fractions. An obscured sky is not a fully cloud-covered sky.

Estimated cloud amount (oktas): 4
Input cover (%): 50
Log text: 50% estimated cover; 4/8 oktas. Not a cloud-height or cloud-type observation.

Select and copy log text

50% estimated cover; 4/8 oktas. Not a cloud-height or cloud-type observation.

Introduction & principle

This teaching converter rounds visible cover to the nearest eighth but reserves 0 for exactly clear and 8 for complete cover. Values between them stay 1–7. Inverse values are nominal eighth percentages, not exact measured coverage. Obscured sky is code 9, not 8 or 100%.

Worked example

50% cover gives 4/8. A tiny nonzero amount gives at least 1/8; 99% remains 7/8. Obscured sky cannot be assigned a cover percentage.

Detailed usage guide

1Choose percent-to-oktas or oktas-to-nominal-percent.
2Enter visible cloud amount, or mark the sky obscured when it cannot be assessed.
3Select the generated text and copy it to your log; retain uncertainty and observer context.

Common problems & FAQ

How is an obscured sky handled?

Mark the sky obscured to generate code 9 without a percentage. Eight oktas means complete visible cloud cover; it does not mean the sky could not be assessed.

Methods & references

Method context and reference

Method reviewed November 4, 2026. These tools support learning and recording, not safety-critical decisions.

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