Open interest is defined as the total number of outstanding option contracts on a given series or a given underlying. Option orders are generally associated with an election of opening or closing and buy or sell. The effect of a given order upon open interest is based upon the elections of both the buyer and seller and is outlined in the table below.
| Buyer | Seller | Open Interest |
| Opening Buy | Opening Sell | Increases |
| Opening Buy | Closing Sell | No Change |
| Opening Sell | Opening Buy | Increases |
| Opening Sell | Closing Buy | No Change |
| Closing Buy | Opening Sell | No Change |
| Closing Buy | Closing Sell | Decreases |
| Closing Sell | Opening Buy | No Change |
| Closing Sell | Closing Buy | Decreases |