Volumetric Dosing

Volumetric dosing is a simple, reliable way to accurately measure substances that are active in the sub-milligram range — doses far too small to weigh on a consumer scale. You dissolve a known mass of a substance in a known volume of liquid; from there the concentration is fixed, and any dose you want becomes a volume you can measure with a syringe or dropper. Use the calculators below to prepare and dose a solution, and always label your solutions with their substance and concentration.

How much solvent do you need?

For a solution withmg/ml, addmg of the substance to—ml of solvent.

What will the concentration be? (mg/ml)

If you putmg of a substance inml of solvent, it will be—mg/ml.

How much do you need to take?

If you have a solution ofmg/ml, and want to takemg, you need to take—ml.

Why?

Some substances are active at sub-milligram doses. That level of precision simply can't be reached with consumer-grade scales, which are rarely accurate below a few milligrams. Volumetric dosing is the standard way to dose the sub-milligram range safely and repeatably.

There are three main reasons to dilute a substance this way:

To bring a substance down into a measurable, safe range below the resolution of your scale.
To start well under a threshold dose, so you can test for adverse reactions before committing to a full dose.
To dilute down to a very low microgram dose as a potency check — for example, to catch a far more potent substance that has been mislabelled as something milder.

Tools

An accurate milligram scale
A graduated cylinder, syringe, or measuring cup with ml markings
A small funnel
Small glass dropper bottles, or a measuring pipette
A suitable solvent — distilled water, or a high-proof spirit, ethanol or propylene glycol where water won't dissolve the substance
A permanent marker for labelling

How?

Research what your substance dissolves in, and at what concentration. Some compounds don't dissolve well in water and need a stronger solvent such as ethanol or propylene glycol; higher target concentrations can need a stronger solvent too.
Weigh out a known mass on an accurate milligram scale. Weigh more than you plan to dose, so your margin for error is larger.
Decide your target concentration and add the matching volume of solvent. For example, 100 mg of substance in 200 ml of solvent gives a concentration of 0.5 mg/ml (500 µg/ml).

concentration = mass of substance ÷ volume of solvent
100 mg ÷ 200 ml = 0.5 mg/ml

Remember: the lower the concentration, the easier and safer it is to dose accurately. Keep your margin for error as large as you need it to be.

Safety

Working with substances active in the sub-milligram range carries a real risk of accidentally dosing yourself while you handle them. Take these precautions seriously.

Wear gloves, a dust mask, and eye protection.
Wipe down every surface as soon as you finish using it.
Never work in an area with a breeze or draft — powder you can't see still moves.
Just because you can't see it does not mean it isn't there. Chemicals active at these amounts can be invisible to the eye.
Never touch your eyes, nose, mouth, or ears while handling powders.
Label every bottle clearly with its substance and concentration. Don't trust your memory — this is vital if anything is stored.
Treat cheap scales, kitchen measuring tools, student glassware and eyedroppers as imprecise. Err on the side of caution every time.

This is harm-reduction and educational information only, provided so that anyone who chooses to handle these substances can do so as safely as possible. Always double-check your own maths, never rely on a single measurement, and be careful. Adapted from community harm-reduction resources.