CBD:THC Ratio Dosage Calculator: Formula and Examples

A CBD:THC ratio dosage calculator converts a ratio and a target milligram dose into milligrams of CBD and THC. It then converts milligrams to milliliters using the bottle volume. The math has two steps: split the dose by ratio, then divide by concentration.

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The formula

Use the ratio parts as the divisor. For a 20:1 product, the parts are 20 CBD and 1 THC. The divisor is 20 + 1 = 21.

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• CBD mg = total dose mg × (CBD parts ÷ total parts)
• THC mg = total dose mg × (THC parts ÷ total parts)
• Concentration mg/mL = total cannabinoid mg in bottle ÷ bottle volume mL
• Dose volume mL = target mg ÷ concentration mg/mL

If the label lists CBD mg and THC mg per bottle, skip the ratio split. Use the listed milligrams and bottle volume.

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Worked examples

1:1 ratio

Bottle: 300 mg total cannabinoids in 30 mL. Target dose: 10 mg total.

Parts: 1 + 1 = 2. CBD = 10 × (1 ÷ 2) = 5 mg. THC = 10 × (1 ÷ 2) = 5 mg. Concentration = 300 mg ÷ 30 mL = 10 mg/mL. Dose volume = 10 mg ÷ 10 mg/mL = 1 mL.

20:1 ratio

Bottle: 420 mg total cannabinoids in 30 mL. Target dose: 21 mg total.

Parts: 20 + 1 = 21. CBD = 21 × (20 ÷ 21) = 20 mg. THC = 21 × (1 ÷ 21) = 1 mg. Concentration = 420 ÷ 30 = 14 mg/mL. Dose volume = 21 ÷ 14 = 1.5 mL.

1:20 ratio

Same 420 mg bottle, 30 mL. Target: 21 mg. CBD = 1 mg. THC = 20 mg. Volume 1.5 mL. This is a high THC dose for a new user.

Dose ranges and limits

No single dose fits all people. Body weight, tolerance, route, and product form change the response. Oral products can take 30 to 120 minutes to show effects. Inhaled products act in minutes. A calculator gives the label dose, not the dose that reaches the bloodstream.

For THC, common low steps are 2.5 mg and 5 mg. A 5 mg THC dose can produce impairment in a new user. For CBD, labels and guides list 10 mg to 50 mg as a common range, with 100 mg to 300 mg used in some clinical settings under guidance. Treat these as ranges, not targets.

Inputs to enter

1. Total CBD mg and total THC mg per bottle, or total cannabinoid mg plus ratio.
2. Bottle volume in mL.
3. Target dose in mg, written as total cannabinoids or as CBD mg.
4. Dose unit: mL, drops, or capsules. Convert drops with the dropper mark volume.

Label example: 1000 mg CBD, 50 mg THC, 30 mL bottle. Ratio = 1000:50 = 20:1. Total = 1050 mg. Concentration = 1050 ÷ 30 = 35 mg/mL. A 10 mg total dose = 10 ÷ 35 = 0.29 mL.

What the label must show

A useful label lists CBD mg, THC mg, bottle volume, batch date, and a test result. Without THC mg, a ratio claim is weak. A 20:1 label on a 1000 mg CBD bottle implies 50 mg THC. If the test shows 10 mg THC, the ratio is 100:1. The calculator output changes with the test value, not the marketing value.

Limits of the calculator

The calculator cannot correct for inaccurate labels. It cannot predict your response. It cannot convert a CBD dose to a THC dose. It cannot set a legal limit. Use it to check math and to compare products, not to decide a starting dose.

Law and safety

Federal law sets the hemp THC limit at 0.3% on a dry weight basis. State rules for CBD and THC differ. Some states cap THC per serving or per package. Check the label and state rules before you use a product. Do not drive after THC. Do not mix THC with alcohol or sedatives. Talk to a clinician if you take prescription drugs, are pregnant, or have a heart condition.