Two serums can both say "niacinamide" on the front and cost about the same per bottle, yet one holds four times as much of the ingredient. gramdang ranks products by what one gram of the named ingredient costs.
A 30 mL serum labeled 10% niacinamide holds 3 g of niacinamide. At 12,000 won, that is 4,000 won per gram. Retinol and retinal are counted in milligrams; everything else in grams.
The seven rules
1
DenominatorThe amount of the ingredient in one container: size × labeled concentration. 1 mL is treated as 1 g.
2
PriceThe selling price shown on the product's Coupang (Korea) page, recorded on the same weekday each week. Multi-packs are divided down to one unit and marked as such. Member-only prices and card discounts are left out.
3
RankPrice ÷ ingredient amount, lowest first. Different forms of an ingredient, such as retinol and retinal, are ranked in separate tables.
4
Where the % comes fromThe product name, the label, or the brand's official statement. In Korea, a cosmetic that puts an ingredient in its product name must state that ingredient's content on the packaging (Enforcement Rule of the Cosmetics Act, Article 19). Products tagged "no % on label" are being re-checked.
5
What is left outEfficacy, safety, skin compatibility, irritation and texture. The tables compare what you pay for the same ingredient and nothing else.
6
ScopeOnly products that disclose their content. Most were found through Coupang search. Products not sold as a single unit on Coupang are listed without a link.
7
No adjustmentsRanks come straight from the formula. They are not changed for commission rates, affiliate status or brand requests. Every removal or corrected number is recorded in the change log on the main page.
What the numbers are not
They are label claims. gramdang has not lab-tested any product.
They do not reflect stabilization, packaging, or breakdown after opening.
They are not a ranking of how well a product works or how gentle it is. A higher concentration can irritate more.
Prices are those posted on the collection date and move with promotions and coupons.
Corrections
If a number is wrong or a product has been reformulated, tell us through the correction form (in Korean; English is fine). Confirmed fixes go into the next weekly update and the change log.
Data files
The labeled content, container size and computed ingredient amount for every listed product (69 products as of 2026-11-13) are available as CSV and JSON. Prices are not included in the files. When quoting, please credit gramdang.com with the update date.
Independence and disclosure
gramdang is run independently of the brands and of Coupang and takes no brand sponsorship. Product links on the Korean ranking page are Coupang Partners affiliate links, and gramdang may earn a commission from purchases made through them. Links that Coupang does not allow are shown as restricted; the product keeps its rank.