Recently, I saw many people in the community asking a question: Why does it cost so much more to buy the same company on the Taiwan stock market versus the US stock market? The key behind this difference lies in the variation in trading units.

First, the conclusion: The US stock market has no concept of "one lot," and the trading unit is simply "one share." But the Taiwan stock market is different; buying stocks is based on "one lot," which equals 1,000 shares. This difference creates completely different entry barriers between the two markets.

Taking TSMC as an example makes this very clear. Suppose the Taiwan stock price is 561 New Taiwan Dollars per share. Buying one lot of TSMC would cost 561 × 1,000 = 560k New Taiwan Dollars. But when the same company is listed on the US stock market, how many shares are in one lot? The US market doesn't have the concept of "lots" at all; trading is directly in shares. So, if TSMC is priced at $95 per share in the US, you only need $95 to buy one share. The entry barrier instantly drops from 560k TWD to less than 3,000 TWD.

This explains why many retail investors feel that US stocks are cheap and Taiwan stocks are expensive. It's not because the companies are fundamentally different, but because of the different trading rules. To allow more people to participate, Taiwan later introduced "odd lot trading," enabling investors to buy between 1 and 999 shares, lowering the capital threshold. However, odd lot trading has less liquidity than full lots, and matching orders can take more time.

The differences between US and Taiwan stocks are not limited to this. The US trading unit is 1 share, while Taiwan's is 1,000 shares; US stocks are priced in US dollars, Taiwan stocks in New Taiwan Dollars; there are no price limit restrictions in either market; transaction fees are basically zero in the US, but Taiwan charges 0.1425%. These details together create a completely different trading experience.

Ultimately, understanding how many shares one lot equals in the US market boils down to recognizing that the design philosophy of trading units in the two markets is different. The US allows buying from just one share, while Taiwan uses one lot (1,000 shares) as the basic unit. If you want to participate in Taiwan stocks at a lower cost, odd lot trading is an option; if you prefer a more flexible trading experience, the US system of trading one share at a time definitely has advantages.