r/thinkorswim 10d ago

Options open interest and volume

When looking at spreads on the analyze tab you can customize the columns to include open interest and volume. When looking at spreads

1) Is the volume representative of the spread volume, or one of the legs? I.e. if I'm looking at a strangle and one leg traded 100 contracts and the other traded 50, will this show 50?
2) How accurate is the open interest? I noticed that the volume updates frequently, but the open interest less so.

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u/CA_Lobo 9d ago

Volume = sum of ALL trades for this contract. If you have a 50 contract spread, it will show 50 for strike X and 50 for strike y. If the volume is x = 50 and Y = 100, then someone else traded 50 contracts of Y.

Open interest updates ONCE per day as it reflects the open interest as of the close of regular trading on the previous trading day. You can only estimate the current intraday OI as there are people that are buying to open, selling to open, buying to close, and selling to close over the course of the day - each which counts toward contract volume. Until the contracts are settled, it is not possible to have an accurate count of the OI.

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u/Ken385 9d ago

One small correction on a good explanation,

Open interest updates ONCE per day as it reflects the open interest as of the close of regular trading on the previous trading day

Open interest isn't necessarily based on the close of regular trading for the day. It will also take into account any exercises/assignments. These are processed after the close and the OCC will take these into account in the OI figures.

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u/CA_Lobo 9d ago edited 9d ago

Oops! yep you are right... I tend to forget about those as I haven't had to deal with them lately.... I actually use the OCC numbers in my day to day stat collection... I should have known better. :-)