Borax Ant Killer Calculator

How borax ant bait works

Borax is a mineral salt, sodium tetraborate, and it works as a slow stomach poison for ants. The key word is slow. A bait that kills on contact gets noticed, and the foragers stop coming. A bait that takes a day or two gets carried back to the nest and fed to the queen and the larvae before anything seems wrong.

That is why the concentration matters so much. Too little and the ants ignore it. Too much and they die on the way home, or the colony detects the poison and quits the trail. The sweet spot is a low dose, roughly 1 part borax to 4 to 9 parts sugar by volume, which lands at about 2 to 5 percent of the finished mix once the water is added.

Borax is the laundry booster in the green box. Boric acid is a related compound sold as an insecticide powder. Both work on ants, and both are toxic if swallowed, so the rules for mixing and placing them are the same. Neither is a contact spray, and neither will help if you only treat the ants you can see.

The standard recipe, scaled

The base recipe makes about 4 cups of sugar bait, which is more than most homes need. The calculator above scales it to any batch size, and the table shows a few common sizes at the standard strength.

Dissolve the borax and sugar in warm water and stir until the liquid runs clear. If the borax will not dissolve, warm the water a little more. Do not add more borax to speed things up, since that is the fastest way to make a bait the ants will refuse. Store leftovers in a labeled jar with a lid, out of reach of children and pets.

Worked example: mixing 2 cups of bait

Say you have a trail of ants along the kitchen counter and you want a small batch, 2 cups, so little is left over.

• Batch size: 2 cups
• Borax at standard strength (3 tbsp per 4 cups): 1 1/2 tbsp
• Sugar: 1/2 cup
• Warm water: 1 1/2 cups
• Borax as a share of the finished mix: about 4.5 percent by volume
• Stations at 1/4 cup each: 8

Mix it in a jar you will not use for food again, and mark the jar. Set the bait out in shallow lids or small dishes, close to the trail but away from pets and bare feet. Expect the ant traffic to increase for the first day, because the colony is recruiting foragers to the new food source. That rise is normal. The drop usually comes on day two or three, and a large colony can take a week or two to die out.

Leave the bait alone while it works. Wiping up the trail or spraying the ants with an insecticide while the bait is out stops the transfer you are counting on. Wait until the ants stop coming, then clean up and seal the entry points you can find.

Sugar bait or protein bait: match the colony

Ants change what they want depending on the season and the species, and the wrong bait gets ignored. Sugar bait is the default and covers most kitchen ants, including odorous house ants and Argentine ants. Protein bait is the answer when sugar fails, and it suits fire ants, carpenter ants and pharaoh ants at certain times of year.

A quick test tells you which to use. Put a dab of honey or sugar water on one side of a card and a dab of peanut butter on the other, and leave it near the trail for 30 minutes. Whichever side the ants gather on is the base to use. If they ignore both, the colony may be feeding somewhere else, or the trail you found is not a feeding trail.

For a protein bait, mix borax into smooth peanut butter or a little canned pet food at the same low concentration, and thin it with a spoonful of water if it is too stiff to spread. The rest of the method is identical: small stations, near the trail, and no cleanup while the bait is working. A protein bait can go rancid in warm weather, so mix it in smaller batches than you would a sugar bait.

Safety around kids, pets and food

Borax and boric acid are pesticides, and a bait station is a small dish of something that looks like food. That combination needs a plan before you mix anything.

• Keep children and pets away from the stations. A small dog that eats the whole batch can get sick, and boric acid is more toxic to cats than to dogs.
• Put the bait inside a covered container with small holes, or behind an appliance where only ants can reach it.
• Never store bait in a food container or a drink bottle. Label the jar and keep it out of the kitchen cabinets.
• Wash your hands after mixing, and clean any spills on counters with soap and water.
• Do not set bait where it can touch food, utensils or dishes.

If someone swallows bait, call Poison Control at 1-800-222-1222 right away and have the container with you so you can read the ingredients. The EPA publishes the safety data for boric acid and borax products, the National Pesticide Information Center answers questions about home pesticide use, and the CDC covers what to do after a poisoning. None of this is medical advice, and a bait that is safe when used as directed is still not safe to eat.

Why the bait sometimes fails

When a borax bait does not work, the cause is usually one of five things. The concentration is wrong, the ants found a better food source, the bait dried out, you cleaned the trail, or you are fighting the wrong ant.

Concentration is the most common. Doubling the borax to speed things up backfires, because ants that die near the bait never make it home, and the colony learns to avoid the spot. Keep the mix at the low end and be patient.

Dried bait stops working because ants cannot carry a solid. Refresh the stations every few days, or set the bait in a spot that stays damp. The other common mistake is competition: if there is a spilled bag of sugar in the pantry or a pet bowl on the floor, the ants have a better offer and will ignore yours. Clean up other food sources first.

Species matters too. Some ants, like carpenter ants, nest in wood and do not rely on the sugar trails you see in a kitchen, so a bait station on the counter will not touch the colony inside the wall. If the bait does nothing for two weeks, it may be time for a pest control professional rather than a stronger mix.