Varroa Mite Calculator
Varroa is the number-one killer of honey bee colonies, and you can only manage what you measure. Enter your alcohol wash or sugar roll below to turn a raw mite count into mites per 100 bees — then see whether the seasonal threshold says to treat, monitor, or hold.
This tool gives product-neutral guidance and defensible seasonal thresholds. It never recommends a specific miticide — for treatment options, see our varroa treatment guide.
Calculate Your Mite Load
About 300 bees (½ cup). The most accurate method — it dislodges nearly every mite, but the sampled bees do not survive.
Jun – Jul · action threshold ≈ 3 mites per 100 bees
At 3.0 mites per 100 bees you are at or above the summer action threshold (3%). Plan a treatment promptly and re-test 2–4 weeks later to confirm it worked.
Summer timing: Mites double roughly every month while brood is heavy. Monitor monthly through summer so you are not surprised when supers come off.
Seasonal Varroa Treatment Thresholds
There is no single magic number. The action level tightens as the season moves toward the winter bees. These ranges follow Honey Bee Health Coalition guidance — treat them as a starting point and confirm with your local extension or bee inspector.
| Season | Months | Watch | Treat |
|---|---|---|---|
| Spring | Mar – May | 1%+ | 2%+ |
| Summer | Jun – Jul | 2%+ | 3%+ |
| Late summer | Aug – Sep | 1%+ | 2%+ |
| Fall | Oct – Nov | 1%+ | 2%+ |
| Winter | Dec – Feb | 2%+ | 3%+ |
Late summer (Aug – Sep)
The most important window of the year. The bees being reared now become your winter bees — mites feeding on them shorten their lifespan and are the leading cause of winter colony loss. Get the load low as supers come off.
Winter (Dec – Feb)
A broodless winter cluster is the one time of year mites have nowhere to hide, which makes a single well-timed treatment unusually effective. Confirm the colony is broodless before treating.
Frequently Asked Questions
What varroa mite level requires treatment?
A common action level is about 2-3 mites per 100 bees for most of the season, tightened to roughly 1-2% around late summer when the winter bees are being reared. These are guidance ranges from the Honey Bee Health Coalition, not hard rules — the right number depends on your region, your bees, and the time of year.
How do I do a varroa mite wash or count?
Collect about a half cup of bees (roughly 300) from a brood frame, taking care not to include the queen. Add alcohol, powdered sugar, or CO₂ to dislodge the mites, then count the mites that come off. Divide the mite count by the number of bees and multiply by 100 to get mites per 100 bees.
Alcohol wash vs sugar roll — which is more accurate?
An alcohol wash is the most accurate because it dislodges almost every mite, but the sampled bees do not survive. A sugar roll lets the bees live and is good for routine monitoring, though it can undercount slightly, so treat a borderline sugar-roll result as the low end of the true load.
When is the most important time to check for varroa mites?
Late summer, as the honey supers come off. The bees reared in late summer and early fall become the long-lived winter bees that carry the colony to spring, and mites feeding on them are the leading cause of winter colony loss. A clean count going into fall is the single best predictor of overwintering success.
How often should I test for varroa mites?
Test at least in spring, again in mid-summer, right before and after any treatment, and once more heading into winter. Monthly monitoring through the active season is better still, because mite populations can double in about a month while brood is heavy.
Keep Going
Varroa Treatment Guide
Above threshold? Compare your treatment options, how to rotate chemistries, and when each one works best.
Read the GuideLog Treatments in QueenGuard
Track mite counts and treatments over time for every hive, and get reminded when it is time to re-test.
Open the Free JournalSugar Syrup Calculator
Feeding after treatment? Get exact 1:1 and 2:1 sugar syrup measurements, plus a winter feeding calculator.
Mix Your SyrupTrack your hives with QueenGuard Journal
Log inspections, monitor colony health, and get smart reminders — free, no credit card. Built for backyard and sideline beekeepers.