Vegan B12 & Protein Plan Calculator
Plan a vegan day: a protein target adjusted for plant-protein quality split across meals, plus a practical B12 supplement dose since plants supply none.
How it works
Protein g/day = weight kg × factor · Per-meal = daily ÷ meals · B12: 2.4 mcg RDA, met via 50–100 mcg daily or 2,000 mcg twice weekly
Vegan diets can meet protein needs easily, but plant protein is a little less digestible and lower in some amino acids, so a small upward nudge from the usual 0.8 g/kg is sensible. Vitamin B12, by contrast, is produced by bacteria and is not reliably present in any plant food, so every vegan needs a supplement or reliably fortified foods. Because absorption falls as a single dose rises, a modest daily dose or a large twice-weekly dose both work well.
Worked example
A 70 kg active vegan at 1.1 g/kg needs about 77 g of protein a day, roughly 26 g across three meals, plus a 50–100 mcg daily B12 tablet to comfortably cover the 2.4 mcg requirement despite partial absorption.
Frequently asked questions
Why do vegans need more protein per kilogram?
Plant proteins are digested slightly less efficiently and some are lower in the amino acid lysine. Nudging the target up modestly — and combining protein sources — covers the difference without any need for large amounts.
Can I get B12 from plant foods?
Not reliably. B12 is made by bacteria, not plants; foods like nutritional yeast or plant milks contain it only when fortified. A supplement is the safest way to avoid a deficiency that develops slowly but can be serious.
Why can a twice-weekly B12 dose be so much larger?
The gut absorbs B12 through a saturable pathway, so only a small fraction of a big dose is taken up. That is why 2,000 mcg twice a week delivers roughly the same net B12 as a small daily tablet.
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Educational estimate for meal planning, not medical or nutrition advice. Serving thresholds and needs vary by person — check with a dietitian for medical diets.