Price per serving beats the cheapest bottle
You pay $0.23 per capsule in a 240-count jar and $0.42 per capsule in a 90-count jar, so the cheapest sticker price is often not the cheapest supplement cost per serving. Two capsules a day finishes a 90-count jar in 45 days, while one a day makes a 240-count last eight months, so you're comparing different things unless you divide the price by the number of servings the label declares.
Magnesium oxide is the usual example. A 500 mg capsule at 60 percent elemental magnesium gives you 300 mg of the mineral, while a 500 mg capsule of magnesium glycinate at 14 percent gives you about 70 mg. Same weight, different dose. If you're paying twice as much for the glycinate form, you may be getting less than a quarter of the mineral, and you'd need four of them to match one oxide dose.
How the comparison actually works
Write down three numbers. Price, servings, and the daily dose the label states. Then divide. A 120-count at $18 with a one-unit serving costs $0.15 a day. A 60-count at $12 with a two-unit serving costs $0.40 a day. The second looks cheaper at the register and costs more than twice as much per day, and you'll be back at the site in a month instead of four.
Bulk only pays when you finish it. Capsules keep roughly two years past the fill date when stored below 25 C, so a 240-count supply is fine if you take it daily and a waste if you take it twice a week. Do the division before you buy bulk. Nobody refunds the last hundred you never opened.
One more thing about your own shelf. Grab two jars from the cupboard and run the same arithmetic on labels you already own. Pick the one you take every morning. A zinc product at 15 mg costs about $0.06 a day if the 120-count was $7, and a chelated zinc at 30 mg costs $0.11 a day if the 90-count was $10. Twice the price, twice the dose, same cost per milligram. You didn't lose anything, and you didn't win anything either.
Liquid and softgel formats break the pattern. A 480 mL liquid at $22 with a 15 mL serving is 32 servings, which is $0.69 a day, and that is nearly five times the capsule rate for the same mineral. Liquids cost more per milligram almost every time because you're paying to ship water. If you don't need the liquid, don't buy the liquid.
Subscription plans change the math too. A 10 percent subscriber discount on a jar you'd buy anyway is a real $0.02 per day saved. The same discount on a jar you'd have skipped because you still had three months left is not a saving at all, and it's the most common way people end up with a cupboard of duplicate stock that expires unopened.
Unit price on the retailer's shelf label does that work in one glance when the store prints it, and most do. The shelf number already divided the price by a standard unit. It's only when the two jars dose differently that you have to correct the figure yourself, which takes ten seconds and saves more than most coupons.
Don't optimize past a cent. If the gap between two honest options is $0.03 a day, you're arguing about $11 over a year, and the twelve months of remembering to take it matter more than the difference. Pick the one you'll finish.
Frequently asked questions
How do I compare two bottles?Show answerHide answer
Divide the price by the number of servings, then check serving size is the same definition.
Why does the cheap one lose?Show answerHide answer
Usually a smaller count or two-a-day dosing, which quietly halves the supply.
Is the expensive one always better?Show answerHide answer
No. Compare the servings, then compare the form and elemental amount.
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
