How to use this CBD dosage calculator
Most beginners take random doses based on the dropper's "recommended serving" and wonder why they don't feel anything. The truth is that CBD dosing isn't one-size-fits-all. Your effective dose depends on your body weight, your previous experience with CBD, and the type of effect you're after. This calculator pulls those three variables together and gives you a starting point that respects the UK Food Standards Agency (FSA) safe daily limit of 70 mg.
To get the most out of it:
- Enter your real weight (use the KG/LBS toggle as you prefer). Body weight matters because CBD is fat-soluble and distributes through your tissues — bigger bodies dilute the dose more.
- Pick the experience level that honestly applies. "Beginner" means you've never taken CBD or you've only tried it a few times. "Experienced" means you've been on a steady protocol for months and know how your body responds.
- Choose the strength that fits your goal. Mild for general background support, moderate for stress and sleep, strong for pain or significant inflammation.
- Select your preferred delivery format (oil, gummy, capsule or vape). This adjusts the practical conversion — how many drops, how many gummies, how many puffs — so you know exactly what to take.
The result you see is a starting point, not a prescription. Stay on this dose for at least 5–7 days before adjusting, because CBD's effects often build cumulatively rather than appearing on day one.
How the calculator works (the science)
The calculation is based on published peer-reviewed research and clinical experience with CBD dosing. The baseline formula is roughly weight (kg) × strength factor, where the strength factor varies between 0.2 mg/kg (mild) and 0.7 mg/kg (strong). For a 70 kg adult, that produces a range of 14 mg to 49 mg per day before experience adjustments.
Experience modifiers then nudge the result up or down. Beginners get a 20% reduction because their endocannabinoid system hasn't been primed — they typically feel the same effects at lower doses. Experienced users get a 20% boost because tolerance builds over time and the receptors become less responsive at the same dose. The final result is then capped at the FSA's 70 mg/day ceiling, which is the upper limit considered safe for healthy adults consuming CBD as a food supplement.
The morning/evening split defaults to a balanced 50/50 distribution. This is the approach most users find optimal because it maintains a steady CBD level in your bloodstream throughout the day rather than producing one big spike and a long valley. If you're using CBD specifically for sleep, you might shift more of the dose to the evening; for daytime focus, weight it toward the morning. The split is a suggestion, not a rule.
Choosing your delivery format
The format you pick has a bigger impact on actual effect than people realise. CBD bioavailability — the percentage of what you take that actually reaches your bloodstream — varies dramatically by method.
Sublingual oil (held under the tongue for 60 seconds before swallowing) has a bioavailability of around 13–35%. It's predictable, fast-acting and gives you fine control over the dose. This is what I personally use as my daily driver. The calculator converts your mg dose into approximate drops based on a standard 1000 mg per 30 ml oil — adjust if your bottle has a different concentration.
Gummies and capsules sit in the 6–15% bioavailability range due to first-pass liver metabolism. They're more convenient and longer-lasting (4–6 hours of effect) but you lose roughly half the dose to digestion. To compensate, the calculator suggests a slightly higher mg total when you select these formats. Pair gummies with fat-containing food for up to 3x absorption boost.
Vaping delivers the highest bioavailability (30–56%) but the shortest duration (2–3 hours). It's the right tool for acute moments — pre-meeting anxiety, sudden pain flare-ups — rather than daily background dosing. The mg recommendation for vape is intentionally lower because more of what you take actually reaches your bloodstream.
Adjusting your dose over time
Your first month with CBD is a calibration period. The dose this calculator suggests is a sensible starting point, but you'll need to adjust based on how your body responds. Here's the protocol I give every reader:
Week 1: Take the suggested dose at the same time(s) every day. Don't change anything else in your routine — no new supplements, no new exercise programmes. Track one variable per day: sleep quality if that's your goal, anxiety level if that's your focus, or pain score if you're treating discomfort. Use a simple 1–10 scale. Don't trust your gut feeling alone — the trend across 7 days tells you more than a single day.
Week 2: Review your numbers. If you're seeing a clear improvement, hold the dose. If nothing's changed and you've experienced no side effects, increase by about 25%. If you've felt drowsy or unusually sleepy, reduce by 25%. The body's response is rarely linear, so small adjustments often work better than dramatic ones.
Week 3–4: By this point you should have a clear sense of whether CBD is doing something for you. Some users see results in week 1; many take 3–4 weeks of consistent dosing before the effects compound enough to be obvious. If you've been at 50 mg+ for two weeks with zero perceptible benefit, CBD may not be your tool. That's a real result — not a failure.
Safety, interactions and when to talk to your GP
CBD is remarkably safe compared to most things in your medicine cabinet. The World Health Organization confirmed in 2018 that CBD has no abuse potential and no documented public health risks at typical doses. But "remarkably safe" doesn't mean zero risk. The most important caveat is drug interactions.
CBD is processed by the same liver enzymes (CYP3A4 and CYP2C19) that metabolise around 60% of all prescription medications. Combining CBD with blood thinners, antidepressants, anti-epilepsy drugs, statins, immunosuppressants or benzodiazepines can intensify or weaken their effects. If you're on any regular prescription, talk to your GP or pharmacist before starting CBD — they'll usually green-light it, but they need to know.
Other times to seek professional input: if you're pregnant or breastfeeding (skip CBD entirely until more data exists); if you have a documented liver condition; if you're scheduled for surgery within two weeks (CBD can interact with anaesthetics); or if you have a history of psychosis or severe mental illness.
For everyone else, the protocol is simple: start at the dose this calculator suggests, take it consistently at the same time every day, pair it with food containing fat for better absorption, and give it at least 4 weeks before judging whether it's working. The dose isn't the only variable — your timing, the product quality, and how you take it all matter. Use this calculator as your starting point, then refine based on real data from your own body.
Oliver's bottom line: The right CBD dose is the smallest one that produces a clear, repeatable effect for you. Most people overshoot and assume more is better — it's not. Start where this calculator suggests, track honestly, and you'll find your sweet spot within a month.