How prices are calculated
ServingPrice compares 25,131 supplements by price per serving rather than bottle price. Price per serving is the sale price divided by servings per container; price per ingredient unit is that value divided again by the ingredient amount in one serving. This page explains the rules used in that calculation, which values are estimated, and what is not verified.
How is price per serving calculated?
Price per serving is the product sale price divided by servings per container. For example, a product with 60 servings priced at 18,000 KRW is 300 KRW per serving. Because bottle price alone cannot compare products of different sizes, this site uses the cost of one serving, not the bottle price, as its primary comparison axis.
How is price per 1mg of an ingredient calculated?
Price per ingredient unit is the price per serving divided by the amount of that ingredient in one serving. If a product costs 300 KRW per serving and contains 200mg of magnesium, that is 1.5 KRW per 1mg of magnesium. Amounts are converted to each ingredient’s base unit (mg, mcg, g) for comparison. The goal is to let you directly compare the cost of taking the same amount of the same ingredient across products.
How are vitamins measured in IU converted?
IU is defined differently for each vitamin, so it cannot be converted with a single ladder; per-ingredient label standards are applied. Vitamin D converts 1 IU to 0.025mcg, and vitamin A converts 1 IU to 0.3mcg RAE. Vitamin E converts 1 IU to 0.67mg for the natural form (d-alpha) or 0.45mg for the synthetic form (dl-alpha), with the form determined from the label notation.
Which values are estimated?
For products whose servings per container is missing from the label data, servings are estimated from the product name and size notation, and the resulting price per serving is marked "est." on screen. Ingredient amounts and sale prices are not estimated; when missing they are left blank and moved to the bottom of the ranking. Missing values are never filled with 0 to force a ranking.
How are products with abnormal amounts handled?
When reading product labels by machine, figures or units from another line can be attached to the wrong ingredient. For example, if a vitamin D amount reads as 2g, that is not a high dose but a physically impossible value. Each ingredient has an upper bound at roughly 3× the highest dose on the market, and values above it are treated as unknown amounts. An inflated amount makes the unit price that much cheaper, pushing a wrong product to the top of the ranking. If the same ingredient appears on several lines for one product and one is within normal range, that value is used instead; otherwise the product is dropped from the unit-price ranking. Some ingredients have separately adjusted bounds so that genuinely high-dose products — such as a vitamin K2 45,000mcg single or a potassium iodide 130mg tablet — are not cut. These bounds were set by inspecting a catalog sample and are not perfect. Also, when a label’s form notation contradicts the assigned ingredient (e.g. classified as vitamin K1 but the notation reads menaquinone), it is counted for neither and excluded from that ingredient’s list.
As of when are the prices?
Prices are as of the most recent collection time, not real time. After collection the whole site is rebuilt to reflect them, and the reference time is published as the lastmod value in sitemap.xml. Displayed prices are the retailer’s listed prices and do not reflect individual discounts, coupons, shipping, or duties. The actual amount charged may differ from the retailer’s screen at the time of purchase.
What is the coverage?
This site covers 25,131 products and 42 per-ingredient comparison pages. Any "cheapest" claim is a fact within this coverage and does not mean the lowest price on the whole market. Discontinued products are removed from the list.
Are the ingredient amounts verified?
Ingredient amounts are copied as declared on the product label and are not results of ingredient analysis. This site does not verify whether the actual content differs from the label. Also, even at equal amounts, differences in absorption or form are not reflected in the price comparison.
How do you earn revenue?
This site may earn a commission when a purchase is made through a link to a retailer. Ranking is determined solely by price per serving and per-unit ingredient price, and is never changed by commission rate. This site is not a party to the sale and has no partnership with any specific manufacturer or retailer.
Ingredients and amounts shown are label-declared values and do not guarantee any medical benefit such as prevention or treatment of disease. Consult a doctor or pharmacist for health decisions.