Varroa Mite Treatment Calculator

Calculate infestation percentage, get a treatment recommendation, and verify post-treatment efficacy. Free. No signup. Nothing gets sent anywhere — all math happens in your browser.

Step 1: Calculate mite infestation

Sample roughly 300 bees (about half a cup) from a brood frame. Shake in alcohol or soapy water, count the mites that fall out, and enter both numbers below.

Standard sample size is 300 bees.

Total mites found in the wash.

Colony phase

Post-harvest; the colony is rearing winter bees.

Treatment thresholds by colony phase: 1% while dormant and during population increase; 2% at population peak and during population decrease (mites per 100 adult bees). Source: Honey Bee Health Coalition, Tools for Varroa Management, 9th edition (June 2026), Table 1. The Coalition calls these conservative estimates and notes thresholds are regional — your apiary inspector or extension service can tell you what applies where you keep bees.

Step 2: Verify treatment efficacy

After a treatment ends, wait 2–4 weeks and repeat the count. Enter your pre-treatment and post-treatment mite counts to calculate the efficacy percentage. Target is ≥ 90%.

Efficacy formula: (pre-count − post-count) ÷ pre-count × 100. A well-applied treatment should hit 90%+. Persistent sub-target results usually indicate resistance (common with Apivar, mostly broken in many regions) or application error.

Free field card: the 14-day wash verification

The calculator checks one count. The card is the two-wash method on one printable page — the ≥90% / <70% verdicts and a per-hive grid for the second wash. One email, then print one per apiary.

One email with the PDF. No spam, unsubscribe any time.

Your post-treatment wash says it didn't work. What do you use next?

If the efficacy figure above came back under 90%, the usual cause is resistance or an application error — and the most common mistake at that point is re-treating with a different product from the same chemical class. Rotate the active ingredient, not the brand name.

  • Amitraz (Apivar and equivalents)

    The class most likely to have failed you. USDA ARS identified amitraz-resistant Varroa destructor as the primary driver behind the record 2024–25 colony losses. A second amitraz product is not a rotation.

  • Formic acid (Formic Pro, MAQS)

    The only widely available option that penetrates capped brood, so it does not need a broodless window. Tightly temperature-bound — check the label's daytime-high range before you commit.

  • Oxalic acid (vaporization or dribble)

    Reaches only phoretic mites, so its efficacy tracks how little capped brood is present — roughly 95% in a genuinely broodless colony, under 50% with brood still capped. That makes it the late-autumn and winter option rather than the October rescue. Work out the label dose per colony.

  • Thymol (Apiguard and equivalents)

    A distinct class from all three above, and also temperature-dependent. Worth checking the label against your forecast before ruling it in or out.

Whatever you rotate to, run a second wash 2–4 weeks after the treatment ends and put the numbers back through the calculator above. An unverified re-treatment is the same gamble that produced the first failure. Always follow the product label — the notes here are guidance, not a substitute for it.

Related reading

Varroa Mite Treatment Guide: When, What & How to Treat

Full guide to oxalic acid, formic acid, Apivar, thymol, and IPM strategy by season.

Oxalic Acid Dosage Calculator

Vaporization and dribble doses per colony, taken from the current US product labels.

Track Treatments in HiveSense

Log mite counts, schedule treatments, get reminders for removal dates — all in one app.

New to beekeeping?

Our beekeeping starter kit guide covers protective gear, hive types, and the smart-sensor options that pair with HiveSense.

Keep every mite count on file

HiveSense logs mite counts per hive, calculates efficacy automatically, and reminds you when the next count is due.

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Read the full treatment guide