Hand Sanitizer Calculator (WHO hand-rub formulations, any batch size)

Understanding the hand sanitizer calculator — concept and principle

This calculator scales the World Health Organization's two hand-rub formulations to any batch size and to the strength of the alcohol and hydrogen peroxide you actually have. It is meant for health facilities, schools or community programmes producing sanitizer locally.

WHO formula 1, 1 litre: with the default inputs the result is ≈ 110 mL water (top up to the 1 L mark).

How it is calculated

Alcohol (mL) = final alcohol % × batch volume (mL) ÷ stock alcohol %

Hydrogen peroxide (mL) = 0.125% × batch volume ÷ stock peroxide %

Glycerol 98% (mL) = 14.5 mL per litre of batch

Water (mL) ≈ batch − alcohol − peroxide − glycerol

Formulation 1 targets 80% ethanol; formulation 2 targets 75% isopropyl alcohol (v/v).
WHO's 10-litre recipes use 8,333 mL of 96% ethanol or 7,515 mL of 99.8% isopropyl alcohol, 417 mL of 3% peroxide and 145 mL of 98% glycerol, topped up with water.

The principle

Alcohol kills many bacteria and viruses by denaturing proteins, and works best at concentrations of roughly 60–90% with some water present. The small amount of hydrogen peroxide inactivates bacterial spores that may contaminate the ingredients or bottles. Glycerol is a humectant that protects the skin from drying with repeated use. Diluting a stronger stock to the target is a simple mass balance: the alcohol volume × stock % must equal the batch volume × final %.

Worked example

Default inputs: formulation 1, 1 L, 96% ethanol, 3% hydrogen peroxide.

Alcohol = 80 × 1,000 ÷ 96 = 833.3 → 833 mL.
Peroxide = 0.125 × 1,000 ÷ 3 = 41.7 mL.
Glycerol = 14.5 mL.
Water ≈ 1,000 − 833.3 − 41.7 − 14.5 = 110.5 → 110 mL; final alcohol 80%.

Each point is the calculator re-run with only “Total amount to make (L)” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Total amount to make (L)	Alcohol (mL)
0.25	208
0.5	417
0.75	625
1	833
1.25	1,042
1.5	1,250
2	1,667

How to read the result

Add the ingredients in order, then fill to the 1 L mark rather than adding exactly the water figure, because alcohol and water shrink slightly when mixed. WHO advises checking the alcohol strength with an alcoholmeter and storing the bottles for 72 hours before use.

Common mistakes

Using alcohol weaker than the target, which cannot reach 80% or 75%.
Adding extra glycerol for a softer feel, which lowers effectiveness.
Mixing near flames, heaters or sparks.

Keep in mind: Alcohol is highly flammable and must be kept away from children and never swallowed. Local production may be regulated; follow national rules and the WHO guide.

Frequently asked questions

Can I use rubbing alcohol at 70%?

Not for these formulas, which need stock stronger than 80% ethanol or 75% isopropyl alcohol.

Why wait 72 hours?

To give the hydrogen peroxide time to inactivate any spores in the alcohol or bottles.

Can I add fragrance?

WHO advises against additives because of possible allergies and effects on the formulation.

Sources: World Health Organization, Guide to Local Production: WHO-recommended Handrub Formulations, revised April 2010

Checked 9 Nov 2026. World Health Organization, Guide to Local Production: WHO-recommended Handrub Formulations, revised April 2010 (formulations 1 and 2, final concentrations, alcoholmeter check, 72-hour quarantine).

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