Every time you buy or sell a share on the Athens Stock Exchange, you encounter a small but real cost that most beginners never notice — not the brokerage commission, but the gap between the price you can buy at and the price you can sell at. That gap is the bid ask spread, and understanding it is one of the most practical things you can do before placing your first trade.
What Is the Bid Ask Spread?
The bid price and the ask price, defined
Think about buying a used car. The seller has a price they want — say €12,000. You’re willing to pay €11,500. The gap between those two numbers is the negotiation space. Stock markets work similarly, except the process is automated and happens in milliseconds.
The bid price is the highest price a buyer is currently willing to pay for a share. The ask price (sometimes called the offer price) is the lowest price a seller is currently willing to accept. At any given moment, the ask is always higher than the bid — that’s the gap you need to understand.
How the spread is calculated
The calculation is straightforward: ask price minus bid price equals the spread.
If a share has an ask of €10.10 and a bid of €10.00, the spread is €0.10. The spread can also be expressed as a percentage of the share price — in this case, 1%. That percentage framing matters a lot when you start comparing stocks, as you’ll see shortly.
Why Does the Spread Exist?
The spread exists because of the people and firms that keep markets running — known as market makers or liquidity providers. These participants continuously quote both a bid price and an ask price for a stock, standing ready to buy from sellers and sell to buyers at any moment. In exchange for that service, and for the risk of holding shares they may not want, they earn the difference between the two prices. The spread is their compensation.
Supply and demand also shape the spread. When many buyers and sellers are active in a stock, competition pushes the bid and ask prices closer together. When interest is thin, the spread widens — less competition, more risk for whoever is making the market.
Narrow vs. Wide Spread: What the Difference Tells You
What causes a narrow spread
High-volume, heavily traded stocks tend to have narrow spreads. Many participants are active on both sides, competition is fierce, and the risk of holding inventory is low. On the Athens Stock Exchange, large-cap stocks like OPAP or National Bank of Greece are good examples. They trade frequently throughout the day, which keeps their spreads tight and makes them cheaper to enter and exit in pure spread terms.
What causes a wide spread
Thinly traded or smaller-cap stocks show wider spreads. Fewer participants mean less competition, and market makers demand more compensation for the risk of sitting on a position that may be hard to unwind. If you notice the gap between bid and ask is noticeably large relative to the share price, treat that as a signal: this stock costs more to trade than the price tag suggests, and you should factor that in before placing an order.
How the Bid Ask Spread Affects Your Returns on ASE Trades
The spread is an immediate, unavoidable cost. The moment you buy at the ask price and the stock hasn’t moved, your position is already worth less — because if you tried to sell right away, you’d only receive the bid price. That difference comes straight out of your return before any brokerage fee is counted.
Here’s a concrete illustration using round numbers. Suppose you buy 500 shares in a liquid blue-chip stock on the ASE at an ask price of €10.10, with a bid of €10.05 — a spread of €0.05, or about 0.5%. Your immediate, unrealised cost from the spread alone is €25. Now compare that to a smaller ASE-listed company trading at the same €10.10 ask but with a bid of only €9.90 — a spread of €0.20, or about 2%. On the same 500 shares, your instant spread cost is €100, before a single cent of brokerage commission.
For a buy-and-hold investor making one or two trades a year, that €100 may feel manageable. For someone trading in and out of the same position several times, those costs stack up quickly. Each round trip — buying at the ask, selling at the bid — means paying the spread twice. A 2% spread means a stock must rise at least 2% just for you to break even on the trade itself. For thinly traded small-caps on the ASE, spreads in the 2–3% range are not unusual, and that’s a meaningful drag on short-term performance.
Greek Shares covers Athens Stock Exchange mechanics in plain language precisely because costs like the bid ask spread are rarely explained to retail investors in Greece before they place their first trade. Knowing this before you open a position puts you ahead of most beginners.
How to Use the Spread When Reading a Stock Quote
When you look up a Greek stock on your broker’s platform or on the Athens Stock Exchange’s own market data pages, you’ll typically see two prices displayed side by side — the bid and the ask — along with the last traded price. The spread is the gap between them.
A few practical points to keep in mind:
- For liquid Greek blue chips, a spread of a few cents on a stock priced in the €5–€20 range is normal and relatively low-cost. You can generally use a market order without worrying much about the spread.
- For smaller or less frequently traded ASE listings, check the spread before you do anything else. If it’s wide — more than 1% of the share price — consider using a limit order instead of a market order. A limit order lets you set the maximum price you’re willing to pay, so you don’t automatically execute at the ask. You might not fill immediately, but you avoid the worst of a wide spread.
- Watch for stale quotes on very illiquid stocks. If there’s very little trading activity, the displayed bid and ask may not reflect where the stock would actually trade if you placed a sizable order.
The general rule: wider spread means more caution needed, and a limit order is your primary tool for managing that cost.
Bid Ask Spread and Long-Term Investing: Should You Worry?
If you’re planning to buy shares in solid Greek companies and hold them for years, the bid ask spread matters much less than it does for active traders. You pay it once when you buy and once when you eventually sell — spread across a long holding period, even a 1–2% spread cost becomes a small fraction of your total return. Research on market microstructure consistently shows that spread costs hit short-term, high-frequency traders far harder than patient, long-term investors.
That said, understanding the spread is still worth your time. It makes you a more informed reader of stock quotes, helps you choose between market and limit orders with confidence, and gives you a clearer picture of what a trade actually costs. It’s one piece of a larger foundation.
If you found this useful, explore the other stock market terminology guides on Greek Shares. Building a solid understanding of how markets work — order types, how prices are set, what liquidity means — before you place your first ASE trade is the kind of preparation that pays off quietly over time.
