Does each trade count once or twice in volume?

In short: We count it once — not twice.

Every trade involves two parties: a buyer and a seller. But even though there are two sides, only one trade takes place — and only one set of shares is exchanged.

Here's how it works:
One person buys 10 shares.
That means someone else is selling 10 shares.
✅ Result: Only 10 shares are counted as volume — not 20.
You're not counting both the buy and sell separately, because they are part of the same transaction.

Think of it like this:
If you sell 1 share and I buy that 1 share from you, it’s one trade.
Even though there are two people involved, only 1 share changed hands.
So, volume = 1, not 2.

Summary
Trading volume reflects the total number of shares traded, not the number of people involved.
Each share traded — no matter how many buyers or sellers — is counted once.
This is a key concept that many beginners overlook, but it’s essential for reading volume data correctly.

Scenario:
Trader A buys 10 shares from Trader B
✅ Volume = 10
Trader A sells the same 10 shares to Trader C
✅ Volume = +10
📊 Total Trading Volume = 20
Even though it’s the same 10 shares, they were involved in two separate trades:
One trade between A and B
One trade between A and C
Each trade is counted separately, because volume measures how many shares change hands, not whether they’re the same shares.

Think of it like this:
If the same dollar bill is spent 5 times in a store, it still counts as 5 separate transactions. Same logic with shares — every trade counts toward volume, even if the shares are just moving between people.

Summary:
Yes, the total trading volume is 20 shares, even though only 10 physical shares were involved — because they were traded twice.