To compare supplement value, divide the current price by the supply you will actually use. Sometimes that means cost per serving; sometimes it means cost per day. The bottle price and the number of capsules on the front are not enough on their own.
This simple calculation helps you compare suitable products fairly. It also gives you a better refill plan, so a lower-looking price does not become a surprise when the bottle runs out sooner than you expected.
Start with the label's serving
Read the serving size and the suggested daily use. Those are related details, but they are not always identical. A product might use more than one serving in a day, while another might have a single daily serving. Write down the routine the directions actually describe before doing the arithmetic.
Supplement labels provide serving and ingredient information that helps you understand the product.[1] Use the current package for the item you intend to buy. A formula, bottle size, or serving can differ from another flavor or a product you ordered previously.
Use the right calculation
| What you want to know | Calculation |
|---|---|
| Servings in a capsule bottle | Unit count divided by units per serving |
| Days of daily use | Unit count divided by units used per day |
| Cost per serving | Current price divided by servings |
| Cost per day | Current price divided by days of use |
For powders, use the labeled servings per container if supplied. Do not estimate a scoop's contents from its appearance or use a scoop from another tub. If directions offer several approaches, clarify the one you are comparing before calculating a supply estimate.
Try a worked example
Imagine Product A costs $24 and contains 60 capsules. Its directions use two capsules daily. The bottle provides about 30 days, so the cost is $24 divided by 30, or $0.80 per day.
Now imagine Product B costs $30 and contains 90 capsules, also used two daily. It provides about 45 days, so the daily cost is about $0.67. Product B has a higher bottle price and a lower cost per day in this example. These are invented arithmetic examples, not current Rethink prices or a claim that the formulas are equivalent.
Practice with real bottle counts
Rethink Magnesium Glycinate lists 90 capsules and a three-capsule daily serving, which provides about 30 days. OLLY Women's Multivitamin Gummies lists 90 gummies and two daily, which provides about 45 days. Open the current product pages for prices, then calculate the cost per day.
These products have different purposes and ingredients, so you should not choose between them as interchangeable substitutes. The examples show why a 90-count label can represent different daily supplies. Use the same method within a category after identifying products that fit your needs.
Put suitability ahead of the cheapest number
A low daily cost is useful only when the product makes sense for your diet, preferences, and routine. Compare ingredient amounts, allergens, serving convenience, and information quality alongside price. A format you never use is poor value even when the arithmetic looks attractive.
Avoid changing the daily amount merely to stretch a bottle or improve its apparent value. Follow the actual directions and your healthcare advice. Also check delivery charges and any purchase terms that affect the final order cost. For a repeat purchase, understand the current terms before choosing that option.
Use the calculation to plan a refill
Once you know the approximate days of use, note a realistic refill point. Do not assume every bottle is a month or a quarter of a year. Recalculate when a package size or serving changes.
If a product page leaves the serving unclear, ask Rethink for the current label. A specific answer can prevent a poor comparison and help you choose a useful purchase with confidence.
Questions shoppers ask
Is cost per serving always cost per day?
No. It depends on how many servings the directions use daily. Keep the two calculations separate.
Should I choose the biggest bottle?
Compare total supply and suitability. A larger container can be useful, but only if it fits the product and routine you actually want.
What if two products have different nutrient amounts?
Record those differences. Equal daily cost does not mean equal formulas, and value includes more than the price calculation.
Keep exploring
- Magnesium Glycinate vs. Citrate: Compare the Form and the Serving
- Gummy Vitamins vs. Tablets and Capsules: Choose Beyond the Flavor
- Buying Supplements Online: A Checklist for a Store You Can Trust
Sources
Sources reviewed October 10, 2026. Product details checked against current Rethink store pages; the package received is the reference for use directions. Research sources do not endorse Rethink products.
Educational information for adults; individual needs vary. Ask your healthcare professional before supplement use if you are pregnant, breastfeeding, taking medication, or managing a medical condition. Dietary supplements are not intended to diagnose, treat, cure, or prevent disease.
