How to Dilute 35% Food Grade Hydrogen Peroxide: A Practical Australian Guide

How to Dilute 35% Food Grade Hydrogen Peroxide: A Practical Australian Guide

Last updated: April 2026

This article is part of our Complete Natural Cleaning Guide. Looking for specific use cases? See our 10 Uses for Food Grade Hydrogen Peroxide.

If you've just picked up a bottle of 35% food grade hydrogen peroxide, the first question is almost always the same: how do I actually use this?

The short answer is that you dilute it. A 500ml bottle of 35% hydrogen peroxide is a concentrate, and one of the reasons it's such a quietly brilliant product is that it stretches further than almost anything else in your cleaning cupboard. A single bottle of Gaiaganic 35% 500ml makes roughly six litres of ready-to-use 3% cleaning solution - which is why people who've made the switch rarely go back to buying dozens of single-use cleaning products.

This guide walks you through exactly how to dilute it, for what, and how to do it safely.

The dilution chart at a glance

Here are the most common dilutions from 35% food grade hydrogen peroxide. Each assumes you're starting with the concentrated Gaiaganic 35% product.

A worked example, because the fractions get confusing fast: if you want to fill a 500ml spray bottle with 3% solution, you'd mix roughly 42ml of 35% hydrogen peroxide with 458ml of water. Close enough is fine - you don't need chemistry-lab precision for surface cleaning.

The golden rule: always add hydrogen peroxide to water

This is the single most important thing to get right. When you're diluting any concentrate, you always pour the concentrate into the water, not the other way around.

With hydrogen peroxide specifically, this keeps the reaction gentle and prevents any chance of splashing or sudden reactions. Fill your bottle with the water first, then slowly add the 35% hydrogen peroxide.

What you'll need

Before you mix anything, have these on hand:

• A dark glass or HDPE plastic spray bottle. Hydrogen peroxide breaks down in sunlight and in contact with certain metals. Amber glass is ideal. Avoid clear plastic, metal, or aluminium containers.
• A measuring jug or syringe marked in millilitres. A 10ml dosing syringe from the chemist works beautifully for small batches.
• Gloves and eye protection when you're handling the 35% concentrate. Once it's diluted to 3%, it's about the same strength as the brown-bottle peroxide from the pharmacy and doesn't need special handling.
• A funnel if you're filling a narrow-necked bottle.

We always recommend labelling the bottle once you've mixed your solution. Write the concentration (3%, 6%, etc.) and the date. Diluted hydrogen peroxide has a shorter shelf life than the concentrate, so knowing when you mixed it is genuinely useful.

Step-by-step: how to make a 3% solution in a 500ml spray bottle

This is the dilution you'll use most often. It's the all-purpose workhorse.

1. Put on gloves and eye protection.
2. Fill your dark glass or HDPE spray bottle with approximately 458ml of cool, clean water. Filtered is better if you have it.
3. Carefully measure out 42ml of 35% hydrogen peroxide - roughly 8 teaspoons, or four tablespoons.
4. Slowly pour the 35% into the water. Don't shake vigorously; a gentle swirl is enough.
5. Screw on the spray top and label the bottle with "3% H₂O₂" and today's date.
6. Store in a cool, dark place (ideally the fridge or a dark cupboard).

That's it. You now have a 500ml spray bottle that replaces a significant chunk of what used to live under your sink.

Common dilutions for common jobs

Kitchen bench and bathroom spray (3%)

Mix as above. Spray onto surfaces, leave for one to two minutes, and wipe clean. No rinsing required, no chemical residue, and completely safe on food preparation surfaces.

Produce wash (3%, diluted further in a bowl)

Add roughly a quarter cup of your 3% solution to a sink or large bowl of cold water. Soak fruit and vegetables for two to five minutes, then rinse with fresh water. This breaks down surface pesticide residues and extends the shelf life of leafy greens and berries noticeably.

Laundry brightener (3%)

Add half a cup of 3% hydrogen peroxide to your washing machine's drum along with your regular detergent. Particularly good for whites, activewear, towels, and anything that's developed a musty smell.

Mould and mildew remover (6%)

For stubborn mould around shower grout, window sills, or damp corners, the 6% dilution is worth making up specifically. Mix 1 part 35% to 5 parts water. Spray directly onto affected areas, leave for at least ten minutes, then scrub. For very stubborn cases, leave for up to an hour before scrubbing.

Indoor plant watering (0.5%)

A very dilute solution added to plant water helps oxygenate the root zone and can discourage fungal root rot. Mix 1 part 35% to 69 parts water, or simply add a teaspoon of your 3% solution to a litre of plant water.

How long does diluted hydrogen peroxide last?

This is worth understanding. The 35% concentrate, stored properly in a cool dark place, will last around a year. Once you dilute it, the clock starts ticking much faster.

As a rough guide:

• 3% solution, stored in dark glass in a cool place: around 1–2 months
• 3% solution, stored in plastic or warmer conditions: 2–4 weeks
• 6% solution: similar to 3% - use within a month
• Very dilute (0.5% or 1%) solutions: use within a week, preferably mix fresh each time

If your diluted solution stops fizzing on a stain or contact with organic matter, it's lost its potency and it's time to mix a fresh batch. The good news: a 500ml bottle of 35% gives you roughly 12 refills of a 3% spray bottle, so you're never really running out.

Safety and storage

At 35%, hydrogen peroxide is a powerful oxidiser and deserves respect.

• Keep the concentrate in the fridge or freezer. It's stable at low temperatures and deteriorates in heat and light.
• Keep it out of reach of children. This applies to both the concentrate and any diluted solutions.
• Never mix it with other cleaning products, particularly anything containing ammonia, vinegar, or bleach. Hydrogen peroxide on its own is clean and safe. Mixed with other chemicals, the reactions can be unpredictable.
• If the 35% contacts your skin, rinse immediately with plenty of cool water. You may notice a temporary whitening or tingling of the skin - this resolves on its own within an hour or two.
• Avoid contact with metal surfaces, particularly aluminium and copper. The oxidation reaction is dramatic.
• Use dark glass or HDPE plastic for storage. Avoid metal lids and containers entirely.

Frequently asked questions

Can I use tap water to dilute it? Yes, though filtered or distilled water gives a slightly longer shelf life because it contains fewer trace minerals that speed up degradation.

What's the difference between 35% food grade and 3% from the chemist? The food grade 35% is free from stabilisers and additives that are added to pharmacy-grade 3% hydrogen peroxide to extend its shelf life on shop shelves. Those stabilisers are fine for first aid but not something most people want near food preparation surfaces or produce. The 35% concentrate is also dramatically more economical - one 500ml bottle replaces roughly twelve 500ml pharmacy bottles.

Do I need to dilute it if I only use it for laundry or mould? Yes. The 35% concentrate is too strong for direct household use. Diluting it to 3% or 6% is what makes it safe and effective for the jobs you'd actually use it for.

Can I buy it already diluted? Yes. We stock a pre-diluted Gaiaganic 3% 500ml for anyone who'd rather skip the mixing step. It's the same food grade product, just ready to use out of the bottle. Many first-time customers start here and move to the 35% concentrate once they're confident with it.

Is there a smaller size of the 35%? Yes. We also stock Gaiaganic 35% in a 200ml bottle - good for first-timers who want to try it before committing to the larger size.

Finding the right format for you

Three options in the Gaiaganic range, all Australian-made and certified food grade:

• Gaiaganic 35% 500ml - best value, roughly six litres of 3% solution per bottle. The choice for regular household users.
• Gaiaganic 35% 200ml - a smaller format for those who want to try the concentrate without committing to a larger bottle.
• Gaiaganic 3% 500ml - pre-diluted and ready to use. The simplest option for first-timers or for people who don't want to handle the concentrate.

Whichever you choose, you're replacing a cupboard full of single-use products with one bottle that handles most of them. That's the quiet satisfaction of this stuff - fewer ingredients, less packaging, and a genuinely effective alternative to conventional cleaners.

Explore the full Gaiaganic range in-store at Santos Organics or online.