A standard shot typically contains 1.5 ounces of liquid in the United States.

Additional details:

• In the US, a "shot" is generally considered to be 1.5 fluid ounces (44 ml).
• In other countries, the size of a shot can vary:
  • UK: usually 25 ml or 35 ml (about 0.85 or 1.2 ounces)
  • Australia: typically 30 ml (about 1 ounce)

So, if you're measuring a shot for a cocktail or drink recipe in the US, use 1.5 ounces as the standard amount.