CALCULATOR

Magnesium Calculator

Your daily magnesium target, an estimate of what your diet supplies, and the elemental supplement dose that closes the gap.

Magnesium plan

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Daily target–

Estimated from food–

Gap to close–

Suggested supplement–

Or close it with food–

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Estimating your magnesium gap

Adult magnesium recommendations sit at roughly 400 to 420 mg daily for men and 310 to 320 mg for women, rising slightly after age 30. National survey data consistently shows average intakes below these figures, particularly in diets low in nuts, seeds, legumes and leafy greens.

This calculator estimates your dietary intake from your eating pattern and shows the gap. The estimate is deliberately rough, because magnesium is spread across many foods rather than concentrated in a few, so a precise figure would require full dietary tracking.

The important detail on the supplement side is elemental content. Supplements list a compound such as magnesium glycinate, and the magnesium inside it is a fraction of that weight. A 500 mg magnesium glycinate capsule may deliver only 50 to 100 mg of actual magnesium, which is why comparing products on the compound weight is misleading.

Targets and the elemental trap

Recommended intakesMen 19-30: 400 mg Men 31+: 420 mg
Women 19-30: 310 mg Women 31+: 320 mg

Supplemental upper limit: about 350 mg elemental, separate from food

The upper limit applies to supplements only because magnesium from food is regulated by absorption and excretion without difficulty. Exceeding it from supplements typically causes diarrhoea rather than serious harm in people with normal kidney function, but kidney disease changes that entirely.

Elemental magnesium by form

Form	Elemental share	Absorption	Digestive effect
Oxide	About 60%	Poor	Laxative
Citrate	About 16%	Good	Mildly laxative
Glycinate	About 14%	Good	Gentle
Malate	About 15%	Good	Gentle
Threonate	About 8%	Good	Gentle, expensive

Note the tension in that table. Oxide has the highest elemental share by weight but the worst absorption, which is why a high number on the label does not translate into magnesium in your bloodstream. Glycinate has a low elemental share, meaning more capsules, but delivers more of what you swallow.

Magnesium in food

Food	Serving	Magnesium
Pumpkin seeds	30 g	156 mg
Chia seeds	30 g	111 mg
Almonds	30 g	80 mg
Spinach, cooked	100 g	87 mg
Cashews	30 g	74 mg
Black beans, cooked	100 g	70 mg
Dark chocolate 70%	30 g	65 mg
Avocado	1 medium	58 mg
Oats, dry	50 g	60 mg
Wholemeal bread	2 slices	46 mg

Who is most likely to be short

Diets built on refined grains and low in nuts, seeds, legumes and greens.
Older adults, who absorb less and excrete more.
People with type 2 diabetes, through increased urinary losses.
People with gastrointestinal conditions affecting absorption, including coeliac and Crohn disease.
Long-term users of proton pump inhibitors, where low magnesium is a documented association.
Heavy alcohol use, which increases excretion.

Blood magnesium is a poor marker of status, because the body maintains serum levels tightly by drawing on bone stores. A normal blood test does not rule out low total-body magnesium, which is one reason intake estimation from diet is a practical starting point.

Frequently asked questions

How much magnesium do I need daily?

Roughly 400 to 420 mg for men and 310 to 320 mg for women, from food and supplements combined.

What is the supplemental upper limit?

About 350 mg of elemental magnesium daily from supplements, separate from food. Higher intakes commonly cause diarrhoea.

Which form absorbs best?

Glycinate and citrate absorb well. Oxide is cheap, poorly absorbed and most likely to cause digestive upset.

Can I get enough from food?

Yes, if you eat nuts, seeds, legumes, wholegrains and leafy greens regularly. Pumpkin seeds alone supply about 150 mg per 30 g.

Sources

National Institutes of Health, Office of Dietary Supplements. Magnesium fact sheet for health professionals. ods.od.nih.gov
Institute of Medicine. Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D and Fluoride, 1997.
Schwalfenberg GK, Genuis SJ. The Importance of Magnesium in Clinical Healthcare. Scientifica, 2017.
National Institutes of Health, Office of Dietary Supplements. Nutrient fact sheets. ods.od.nih.gov
NHS. Nutrition and health guidance. nhs.uk
US Departments of Agriculture and Health and Human Services. Dietary Guidelines for Americans, 2025-2030. dietaryguidelines.gov

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General information, not medical advice. Consult a qualified professional before changing your diet, especially with a medical condition.