Mix the right mold cleaning solution
Most mold cleaning advice online gives a ratio for a gallon and leaves you doing math over a spray bottle. This calculator scales bleach, vinegar, hydrogen peroxide, borax, and detergent mixes to whatever you're filling, and tells you how long to leave it on.
Your mix
Wear gloves, eye protection, and an N95. Open a window. Cleaning removes surface growth. It doesn't fix the moisture that caused it, and it can't reach mold inside porous material.
Ratios at a glance
| Cleaner | Per gallon of water | Per 32 oz spray bottle | Contact time | Best on |
|---|---|---|---|---|
| Detergent | 1 tbsp to 1/4 cup | 1 tsp | Scrub | Any hard surface. EPA's default. |
| Bleach | Up to 1 cup | 1/4 cup | 10 min | Tile, tub, glass, concrete. Never porous surfaces. |
| Vinegar | Undiluted | Undiluted | 60 min | Grout, caulk, appliances, painted walls |
| Hydrogen peroxide 3% | Undiluted | Undiluted | 10 to 15 min | Fixtures, painted surfaces, fabric (test first) |
| Borax | 1 cup | 1/4 cup | Leave on | Wood trim, painted walls, concrete |
| Baking soda | 1/2 cup | 2 tbsp | Scrub | Fabric, seals, odor |
Frequently asked questions
What is the right bleach to water ratio for mold?
Up to 1 cup of regular household bleach per gallon of water, which is 1/4 cup in a 32 oz spray bottle. That is the CDC's post-flood cleaning ratio. Stronger does not work better, it just makes more fumes. And bleach only belongs on hard, non-porous surfaces.
Why does the EPA not recommend bleach for mold?
The EPA says routine use of bleach is not recommended for mold cleanup. Detergent and water physically removes the growth. Bleach on porous material kills the surface, the water in the mix soaks in, and the mold below regrows. It also produces fumes and damages finishes.
Which is better, vinegar or bleach?
For most household jobs, vinegar. It soaks into grout and caulk where bleach sits on top, it is safer to handle, and it works on painted walls. Bleach wins for disinfecting a hard surface after sewage or floodwater, once the surface is already clean.
Can I mix vinegar and hydrogen peroxide?
Not in the same bottle. Together they form peracetic acid, which irritates skin and lungs. Use one, rinse, then the other if you want both. Never mix anything with bleach.
When is cleaning not enough?
When the patch is over about 10 square feet, when the material is drywall, insulation, or carpet padding, when there was a leak or flood, or when it comes back after you clean it. That is a moisture problem or a hidden growth problem, and no spray fixes either one. Use Do I need a pro? to check.
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