You flip over a packet of chips and the label says 800 mg of sodium per 100 g. Is that a lot of salt? Not obviously, because sodium and salt are not the same number. Here is the simple formula that turns any sodium figure into grams of salt, with a real example.
Sodium and salt are not the same thing
Refined table salt is about 97 to 99 percent sodium chloride, a compound of sodium and chlorine. Only the sodium part is what nutrition labels and health guidelines track.
The key number to remember: salt is only about 39.3% sodium by weight. The rest is mostly chlorine. So a gram of salt gives you well under half a gram of sodium, and a label that lists sodium is showing you a number roughly two and a half times smaller than the salt it represents.
The formula: from sodium to salt and back
Because salt is 39.3% sodium, the conversion works in both directions:
- Salt (g) = sodium (mg) ÷ 393
- Sodium (mg) = salt (g) × 393
In plain words: divide the sodium on a label by 393 to get the salt you are actually eating (this also converts milligrams into grams).
For a quick mental version, multiply sodium by 2.5 and switch the unit from milligrams to grams at the end. Salt is “just under 40%” sodium, and 1 ÷ 0.4 = 2.5. The exact factor is closer to 2.54, so the shortcut lands about 2% low, which is fine for everyday label reading.
A real example: one packet of chips
Potato chips carry around 800 mg of sodium per 100 g, compared with just 7 mg for plain potatoes. Here is how to read that:
- Per 100 g: 800 ÷ 393 ≈ 2.04 g of salt (shortcut: 800 × 2.5 = 2,000, so about 2 g).
- Say your packet weighs 50 g. That is half of 100 g, so 400 mg of sodium, or about 1.02 g of salt.
- Compare with the daily limit. The World Health Organization recommends adults consume less than 2,000 mg of sodium a day, which equals 5 g of salt. 400 ÷ 2,000 = 20%.
So one small packet uses up about a fifth of the day’s recommended maximum, before you have eaten anything else.
Now the other direction: a teaspoon of salt
A level teaspoon of salt weighs about 6 g. Using the formula: 6 × 393 = 2,358 mg of sodium, roughly 2,400 mg. That single teaspoon is already above the WHO limit of 2,000 mg of sodium for the whole day. If a recipe for four calls for one teaspoon, each serving carries about 590 mg of sodium from that salt alone.
The same food, very different numbers
Processing changes the sodium content dramatically. Per 100 g:
- Pork: 63 mg of sodium, while bacon has 1,480 mg (about 3.77 g of salt)
- Herring: 67 mg, while kipper, its preserved form, has 990 mg (about 2.52 g of salt)
- Potatoes: 7 mg, while potato chips have 800 mg (about 2.04 g of salt)
This matters because most sodium does not come from the salt shaker. In the United States, 75% of the sodium people eat comes from processed and restaurant food, and only 11% from cooking and table use. Sauces count too: soy sauce, fish sauce and oyster sauce are all high in sodium and play the same role as table salt in many cuisines.
Common mistakes when reading sodium
- Reading sodium as salt. A food listing 2 g of sodium contains about 5.1 g of salt, not 2 g. Mixing the two underestimates your salt by a factor of about 2.5.
- Mixing up mg and g. Sodium is usually listed in milligrams, salt advice is usually given in grams. 2,000 mg is 2 g of sodium, which is 5 g of salt.
- Forgetting the portion. Values per 100 g only apply if you eat 100 g. Scale them to what is actually on your plate.
- Using one limit for everyone. The WHO figure is 2,000 mg of sodium. United States guidelines suggest no more than 1,500 mg a day for people with hypertension and for middle-aged and older adults.
Lower is not automatically better without limit, either. As one body of evidence puts it, “the association between sodium consumption and cardiovascular disease or mortality is U-shaped, with increased risk at both high and low sodium intake.” The body does need some sodium for nerves, muscles and fluid balance.
This guide explains how to read a label and is not medical or dietary advice. If you have high blood pressure or kidney disease, ask your doctor what sodium target is right for you.
