Magnesium calculator
Find your UK daily amount, see how much magnesium a supplement label really gives you, and which form suits what you want it for.
Your daily amount
- Your daily amount (UK)
- – mg
- What labels count as 100%
- 375 mg
- Most from supplements (NHS)
- 400 mg
What your label really gives you
Magnesium comes joined to another substance, which makes up most of the weight. Pick the form and the amount of it on the label.
Which form suits you
Three forms in one daily dose
Triple Magnesium gives 301 mg of magnesium a day from glycinate, citrate and malate.
See Triple MagnesiumHow much magnesium you need each day
The UK's reference amounts (Department of Health, 1991, used in the Government Dietary Recommendations) are set to cover the needs of almost everyone.
| Age | Women | Men |
|---|---|---|
| 1 to 3 years | 85 mg | 85 mg |
| 4 to 6 years | 120 mg | 120 mg |
| 7 to 10 years | 200 mg | 200 mg |
| 11 to 14 years | 280 mg | 280 mg |
| 15 to 18 years | 300 mg | 300 mg |
| 19 to 64 years | 270 mg | 300 mg |
| 65 and over | 270 mg | 300 mg |
No increase in pregnancy; 50 mg more a day when breastfeeding.
How much magnesium is in each form
Our own sums from each compound's chemical formula. Real ingredients vary with how they're made.
| Form | Magnesium in 500 mg | Good to know |
|---|---|---|
| Glycinate (bisglycinate) | About 70 mg | Gentle on the stomach; used in a recent sleep trial. |
| Citrate | About 75 mg | Well absorbed; larger amounts can loosen stools. |
| Malate | About 65 mg | A common everyday form, usually easy on the stomach. |
| L-threonate | About 40 mg | Early research on memory; gives little magnesium per capsule. |
| Oxide | About 300 mg | The most magnesium per tablet, but less well absorbed and more likely to loosen stools. |
Labels state magnesium compounds in different ways, so the label's own "magnesium" figure always wins.
Foods high in magnesium
The NHS says you should be able to get all the magnesium you need from a varied diet.
| Food | Portion | Magnesium | Of your day |
|---|---|---|---|
| Brazil nuts | A small handful (30 g) | 123 mg | |
| Brown rice, boiled | A portion (180 g) | 86 mg | |
| Pumpkin seeds | A small handful (30 g) | 81 mg | |
| Almonds | A small handful (30 g) | 81 mg | |
| Cashew nuts | A small handful (30 g) | 81 mg | |
| Peanuts, unsalted | A small handful (30 g) | 63 mg | |
| Baked potato with skin | 1 medium (220 g) | 59 mg | |
| Chickpeas, canned | 3 heaped tablespoons (120 g) | 53 mg | |
| Red kidney beans, boiled | 3 heaped tablespoons (120 g) | 48 mg | |
| Porridge oats | 40 g, before cooking | 46 mg | |
| Salmon, baked | A fillet (140 g) | 42 mg | |
| Spinach, boiled | 80 g | 27 mg | |
| Wholemeal bread | 1 slice (40 g) | 26 mg | |
| Semi-skimmed milk | A glass (200 ml) | 23 mg | |
| Banana | 1 small (80 g) | 22 mg | |
| Avocado | Half (80 g) | 22 mg | |
| Low-fat plain yoghurt | A pot (120 g) | 19 mg | |
| Plain chocolate (36 to 50% cocoa) | 4 small squares (20 g) | 18 mg | |
| Tofu, steamed | 80 g | 18 mg |
Amounts from the UK's Composition of Foods dataset, per portion.
When to take magnesium
Any time of day works, so pick a time you'll remember. Take it with food if it upsets your stomach. If you take more than one capsule, splitting them across the day can be gentler. Many people take glycinate in the evening as part of winding down.
Keep magnesium two hours or more away from some antibiotics and osteoporosis medicines, and check with a pharmacist if you take any regular medicine.
Sources
- NHS. Vitamins and minerals: others (magnesium). nhs.uk
- Public Health England (2016). Government Dietary Recommendations: government recommendations for energy and nutrients for males and females aged 1 to 18 years and 19+ years.
- Department of Health (1991). Dietary Reference Values for Food Energy and Nutrients for the United Kingdom. Report on Health and Social Subjects 41. HMSO.
- British Nutrition Foundation (2021). Nutrition requirements.
- National Diet and Nutrition Survey: years 2019 to 2023. GOV.UK.
- Regulation (EU) No 1169/2011 on the provision of food information to consumers, Annex XIII Part A (as retained in UK law).
- Expert Group on Vitamins and Minerals (2003). Safe Upper Levels for Vitamins and Minerals. Food Standards Agency.
- Public Health England (2021). Composition of Foods Integrated Dataset (CoFID), 1.4 Inorganics.
- British Nutrition Foundation (2019). Find your balance: get portion wise.
Read next
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Magnesium glycinate: the complete guideMagnesium glycinate explained: what it's good for, how much magnesium UK adults need, which form suits you and what the research shows.Magnesium questions
Short answers, based on NHS guidance and published research.
How much magnesium do you need per day?
In the UK, men need 300 mg of magnesium a day and women 270 mg. Teenagers aged 15 to 18 need 300 mg, and children need 85 mg to 280 mg depending on age.
How much magnesium per day for a woman?
Women aged 19 and over need 270 mg a day in the UK. There's no increase in pregnancy, and 50 mg more a day while breastfeeding, so 320 mg. On average, women in the UK get 224 mg a day from food.
Is 500mg of magnesium too much?
It depends what the 500 mg refers to. The NHS says 400 mg or less a day of magnesium from supplements is unlikely to cause any harm, and more can cause diarrhoea. But 500 mg of a compound such as magnesium glycinate gives only about 70 mg of magnesium itself, so check the magnesium figure on the label.
What foods have the most magnesium?
Nuts, seeds, wholegrains and beans. A small handful (30 g) of Brazil nuts has about 123 mg, and the same of pumpkin seeds, almonds or cashews about 81 mg. A portion of boiled brown rice has about 86 mg and a baked potato with its skin about 59 mg.
Which magnesium is best?
It depends on what you want it for. Glycinate is gentle on the stomach, citrate is well absorbed but can loosen stools, malate is a common everyday form and threonate has early research on memory. Oxide packs the most magnesium into a tablet but is absorbed less well.
When is the best time to take magnesium?
Any time of day works, so pick a time you'll remember. Taking it with food can be gentler on the stomach, and many people take it in the evening. Keep it at least two hours away from some antibiotics and osteoporosis medicines.
What is elemental magnesium?
It's the magnesium itself. Supplements use magnesium joined to another substance, such as glycine in magnesium glycinate, so most of a compound's weight isn't magnesium. Step 2 of the calculator works out the magnesium in each form.
What does %NRV mean on a magnesium label?
Labels compare the magnesium with a Nutrient Reference Value of 375 mg, the same for everyone, so 150 mg shows as 40% NRV. Your own UK daily amount can be higher or lower than the NRV.