Oxalic Acid Dosage Calculator
Work out the right oxalic acid dose for dribble, vaporization, or extended-release treatment, scaled to your colonies and based on the EPA product label.
Oxalic acid is cheap, hits phoretic mites hard, and does not build up in your wax. The trick is getting the dose right for the way you apply it. Pick a method below and this calculator gives you the amounts to weigh and mix, scaled to how many colonies you're treating, based on the EPA product label.
Calculator
Application method
Your colonies
A seam is the gap between two frames that has bees in it. The label is 5 mL per occupied seam per box, capped at 50 mL per colony.
Dribble: mix 1.8 g into 50 mL syrup
Capped at the 50 mL per colony label maximum, no matter how many brood chambers.
Follow your product label and wear PPE
These figures follow the EPA-approved oxalic acid label, but the label on your product and your local regulations always govern. Oxalic acid is corrosive: wear acid-resistant gloves and eye protection, and use an acid-gas respirator when vaporizing.
Assumptions & Notes
- Dribble & vaporization figures follow the EPA Api-Bioxal label (rev. 2025-06-24): 35 g per litre of 1:1 syrup, 5 mL per occupied seam per box (max 50 mL/colony); 4.0 g per brood chamber for vapor.
- The per-chamber vapor dose is adjustable because labels differ (older Api-Bioxal 1.0 g, EZ-OX 2 g/box).
- Extended-release figures follow Randy Oliver's OA/glycerin method (scientificbeekeeping.com): 1:1 OA-to-glycerin by weight, ~50 g OA per double-deep hive over ~60 sq in of matrix.
- This tool sizes a dose; it is not a substitute for the product label or local law.
The three ways to apply oxalic acid
Dribble
Trickle an oxalic and syrup solution over the bees with a syringe. Simple, no special gear, best in a broodless period.
Vaporize (OAV)
Heat dry crystals so they sublimate and coat the colony. Very effective on phoretic mites. Needs a vaporizer and a respirator.
Extended-release
OA and glycerin pads that release slowly over weeks. The only oxalic method that works well with brood present.
Why timing matters
Dribble and vaporization knock down mites for only about three days, and they can't touch mites sealed inside capped brood. That is why they work best during a broodless window, like late fall, a winter cluster, packages, or freshly hived swarms, or when repeated at intervals. If you treat a brood-right colony once with dribble or vapor, most of the mites are protected under cappings and survive.
Randy Oliver's extended-release glycerin method gets around this by dosing the colony slowly for 40 to 75 days, so mites emerging from brood keep meeting oxalic acid. It can go on at honey super time and reach roughly 95% knockdown over a season, which is why it has caught on, but check its regulatory status where you live and only use a registered product.
Sources: EPA Api-Bioxal product label (Reg. No. 73291-2) and Randy Oliver, Scientific Beekeeping: Oxalic Acid Treatment Table.
This is dosing math, not label advice
Frequently Asked Questions
How much oxalic acid do I use for a dribble?
The EPA Api-Bioxal label dissolves 35 g of product in 1 litre of 1:1 sugar water, then you trickle 5 mL of that solution onto the bees in each occupied seam of each brood box, up to a maximum of 50 mL per colony. This calculator mixes the batch and applies the per-colony cap for you.
How many grams per brood box for vaporization?
The current EPA Api-Bioxal label (2025) specifies 4.0 g per brood chamber. Important: older Api-Bioxal labels (2021, 2024) said 1.0 g, EZ-OX tablets are 2 g per deep box, and other products differ. The per-chamber dose is adjustable here, so set it to match the label on the product you actually own.
When does oxalic acid work best?
Dribble and vaporization only kill phoretic (riding) mites and have no effect on mites sealed in brood, so they work best during a broodless period such as late fall, winter, packages, or swarms, or repeated at intervals. Extended-release glycerin treatments work over several weeks and can be used while brood is present.
What is the extended-release / glycerin method?
It's Randy Oliver's approach (scientificbeekeeping.com): oxalic acid dihydrate dissolved 1:1 by weight in glycerin and absorbed into a cellulose matrix (sponges, shop towels, or chipboard strips), roughly 50 g of OA per double-deep hive. Unlike dribble and vapor, it works for 40 to 75 days even with brood present, so it can go on at honey-super time. Its regulatory status varies, so only use a registered product and follow its label.
Is oxalic acid safe to use with honey supers on?
Follow your product label. Oxalic acid is generally used during low-brood periods rather than on producing colonies, and extended-release pads must be kept separated from honey you intend to extract. Always defer to the label and your local regulations.