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Varroa mite wash calculator
Enter the mites counted and the number of adult bees in your wash sample. Get a comparable result for your hive records.
Your measurements
Use your wash sample count. Around 300 bees is a common starting sample.
Results update as you edit. Decimal points and commas are accepted.
Your result
Mites per 100 adult bees
2%6 / 300 × 100One extra mite changes the rate by
0.333 percentage pointsUse your local guidance, colony phase and treatment history to interpret this result.
How it works
One sample. A clearly defined rate.
Divide the mite count by the number of sampled adult bees, then multiply by 100. For example, 9 mites in 300 bees gives 3 mites per 100 bees, commonly written as 3%. This measures mites relative to the sampled adult bees, not all mites in a colony.
Further guidance: Honey Bee Health Coalition · Varroa Management
Useful to know
Why is 300 bees the starting sample size?
Around 300 adult bees is a commonly used wash sample. Enter the best available count for your own sample. A smaller sample is more sensitive to a single additional mite; the calculator shows that increment.
Does the percentage tell me whether to treat?
Use the result with regional guidance, colony phase, season and treatment history. A single universal threshold would be misleading here. The linked Honey Bee Health Coalition guidance explains sampling and management decisions.
Can I enter a sticky-board mite count?
No. Natural mite fall is a count over time, not a count from a known sample of adult bees. Do not use it with this formula. A zero wash count also does not prove that a colony is mite-free.