Melatonin dosage calculator
Most melatonin on US shelves comes in 3, 5 or 10 mg tablets, often ten times what the research supports. Pick what you are using it for and your age group, and the calculator gives the dose the research actually supports. You can enter your weight too, but it will not change the answer, and the page explains why.
Useful range 0.5 mg–3 mg. Little evidence of extra benefit above 3 mg.
About 60–90 minutes before bed, in dim light.
The average effect on sleep onset is modest: minutes, not hours. If 3 mg does nothing, more is very unlikely to help.
General information, not medical advice. If you take prescription medication, are pregnant or breastfeeding, or have a sleep disorder, check with a doctor or pharmacist first.
Why weight is the wrong input
Search for a melatonin calculator and you will find plenty that ask for your weight and return something like 0.05 mg per kilogram. It looks rigorous. It is borrowed from how drugs like paracetamol are dosed, where the amount in your blood scales with body size and the effect scales with the amount.
Melatonin does not work that way. It is a timing signal read by receptors in the suprachiasmatic nucleus, and those receptors respond fully at blood levels your own pineal gland produces every night. Researchers at MIT found that around 0.3 mg taken by mouth already recreates that natural peak (Zhdanova et al., 2001). Past that point, more melatonin does not mean more signal. It means the signal lasts into the morning, which is where the grogginess comes from.
The dose depends on the job
Shifting your body clock earlier needs the least. In a controlled trial, 0.5 mg advanced the circadian rhythm as much as 3 mg when both were taken in the right window, about five hours before bedtime (Burgess et al., 2010). Here timing is everything, and the melatonin timing calculator works out the exact hour.
Falling asleep faster is the most common reason people reach for it, and the one where expectations need managing. A meta-analysis of 19 trials put the average gain at about 7 minutes faster sleep onset and 8 minutes more total sleep (Ferracioli-Oda et al., 2013). Real, but small. The American Academy of Sleep Medicine goes further and advises against melatonin as a treatment for chronic insomnia (Sateia et al., 2017); for that, CBT-I has much stronger evidence.
Jet lag is where melatonin has its best track record. The Cochrane review found doses between 0.5 and 5 mg effective for eastward travel across five or more time zones, with no extra benefit above 5 mg (Herxheimer & Petrie, Cochrane).
What is actually in the bottle
In the US, melatonin is sold as a supplement, so nobody checks the label before it reaches the shelf. When researchers tested 31 products, the real content ranged from 83% below to 478% above what was printed, and a quarter contained serotonin (Erland & Saxena, 2017). At 10 mg that error is just more excess. At 0.5 mg it can be the difference between a dose and no dose, which is a good reason to buy a pharmaceutical-grade or third-party-tested product.
When to skip it or ask first
Children are the clearest case. Paediatric use is a clinical decision, and accidental ingestions reported to US poison centres rose roughly 530% between 2012 and 2021 (Lelak et al., 2022), largely from gummies. The other cases are pregnancy, where safety data is thin, and medications that interact with it. Blood thinners, sedatives and immunosuppressants are the usual list, and the antidepressant fluvoxamine blocks the enzyme that clears melatonin, raising its levels many times over.
Frequently asked questions
Should melatonin be dosed by body weight?
Not for adults. Melatonin acts on receptors in the brain’s master clock that respond to very low blood levels. An oral dose of roughly 0.1–0.3 mg already reproduces a normal night-time peak, so a 100 kg adult does not need more than a 60 kg adult. Per-kilogram dosing exists only in some paediatric clinical protocols, which a doctor sets.
What is the best melatonin dose for sleep?
Start at 0.5 mg about an hour before bed. If nothing changes after a few nights, 1–3 mg is a reasonable ceiling. A 2013 meta-analysis found melatonin shortens the time to fall asleep by about 7 minutes on average, so expect a nudge, not a knockout. Adults over 65 often do best on 0.3 mg.
Is 10 mg of melatonin too much?
It is far more than you need. 10 mg pushes blood levels dozens of times above the natural peak without improving sleep, and the extra tends to show up as morning grogginess, headaches and vivid dreams. For jet lag, the Cochrane review found no added benefit above 5 mg.
How much melatonin should I take for jet lag?
Flying east across five or more time zones: 0.5 mg at local bedtime on arrival, for two to four nights. If the first night does nothing, move up toward 3–5 mg. Flying west, melatonin usually matters less than getting evening light.
How much melatonin can I give my child?
This calculator does not give a number for under-18s on purpose. Melatonin use in children has risen sharply, and so have accidental overdoses: US poison-centre reports of paediatric melatonin ingestions grew about 530% from 2012 to 2021. A paediatrician should decide whether it is appropriate, the dose and the duration.
Does the dose on the label match what is in the bottle?
Often not. A 2017 analysis of 31 melatonin supplements found actual content ranged from 83% below to 478% above the label, and some products contained serotonin. Pharmaceutical-grade or third-party-tested products are more reliable, which matters most at low doses.