An ADR premium tells you how far the US-traded depositary share is priced above or below the currency-adjusted value of the underlying foreign share. The arithmetic is short. The difficult part is making sure the two prices represent the same ownership amount and the same currency before comparing them.
For SKHY, 10 American Depositary Shares represent one SK Hynix ordinary share. A direct comparison between one SKHY price in US dollars and one 000660 price in Korean won is therefore invalid.
The SKHY ADR premium formula
The calculator first converts the US ADR price into the implied Korean-won value of one underlying ordinary share:
It then compares that implied value with the latest available price of Korea-listed 000660:
The same calculation can be written in one line:
What each input means
| Input | Unit | Why it is needed |
|---|---|---|
| SKHY price | USD per ADS | The market price of one SK Hynix depositary share on Nasdaq. |
| USD/KRW | KRW per USD | Converts the dollar ADR price into Korean won. For example, 1,491 means one US dollar equals 1,491 won. |
| ADS ratio | 10 ADS per share | Scales one SKHY ADS to the ownership represented by one Korean ordinary share. |
| 000660 price | KRW per share | The market price of one SK Hynix common share on the Korea Exchange. |
The ADS ratio is not an estimate. The final SK Hynix prospectus filed with the SEC states that each ADS represents one-tenth of one common share. That is why the US price is multiplied by 10.
Worked example: July 14, 2026
This historical snapshot uses SKHY at $193.92, 000660 at ₩1,913,000, and USD/KRW at 1,491.00. These are historical observations used to demonstrate the calculation; they are not current quotes.
Step 1: Convert one SKHY ADS into Korean won
Multiplying by USD/KRW removes the currency mismatch. Both sides of the eventual comparison will now be expressed in Korean won.
Step 2: Match the ownership unit
One ADS represents only one-tenth of an ordinary share. Multiplying by 10 gives the value implied by ten SKHY ADS, which corresponds to one underlying Korean share.
Step 3: Compare the implied value with 000660
US-implied Korea share value: ₩2,891,347.20
Observed 000660 share price: ₩1,913,000
₩2,891,347.20 ÷ ₩1,913,000 − 1 = 0.5114203868
+51.14%
In this snapshot, SKHY was priced 51.14% above its Korea-equivalent value before fees, taxes, spreads or execution constraints.
A second way to check the result
You can reverse the calculation by asking what one SKHY ADS would be worth if it exactly matched 000660:
Now compare the observed ADR price with that parity value:
Both methods should produce the same answer apart from rounding. If they do not, check the direction of the exchange rate and the ADS ratio.
What a positive or negative result means
- Positive premium: SKHY is priced above the Korea-implied parity value.
- Zero: the two observations are at theoretical currency-adjusted parity.
- Negative premium: SKHY is priced below the Korea-implied parity value, often described as an ADR discount.
A premium describes the relationship between the displayed observations. It does not say that either security is correctly valued, and it does not predict which price will move next.
Why the displayed premium is not free arbitrage
Nasdaq and the Korea Exchange generally do not trade at the same time. A current US quote may be compared with Korea's latest close, while a current Korean quote may be compared with the previous US session. News and foreign-exchange moves can therefore reprice one market while the other is closed.
Even when both values appear attractive, depositary conversion procedures, settlement timing, bid-ask spreads, taxes, depositary fees, stock borrowing and short-sale restrictions can prevent an investor from capturing the displayed gap. Read the quote timestamps before interpreting any result.
Common calculation mistakes
- Comparing the raw prices. $193.92 and ₩1,913,000 cannot be compared until their currencies and ownership units match.
- Using the exchange rate backward. When USD/KRW is quoted as won per dollar, convert dollars to won by multiplying.
- Ignoring the 10-to-1 ratio. One SKHY ADS is one-tenth of one ordinary share, not one full 000660 share.
- Rounding too early. Keep the unrounded converted value through the final division, then round the percentage for display.
- Treating stale prices as synchronized. Check the market session, source time, holidays and trading halts.
Use the live calculator
The SKHY Premium Calculator applies this formula to the latest available SKHY, 000660 and USD/KRW observations. It retains closed-market values with their source times, so the screen can show exactly which sessions are being compared.
For data sources, refresh timing and missing-data rules, read the methodology. For background on the security itself, see the SK Hynix ADR and ADS ratio guide. Historical observations are available on the premium history page.