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Overnight gap calculator: estimate the SPY open from ES

ES futures keep trading after SPY closes. This calculator converts the overnight ES move into an approximate SPY gap so you can frame the open before the 9:30 ET bell.

How to use it

  1. Enter the prior SPY close.
  2. Enter how many points ES has moved since the SPY close (negative if lower).
  3. Leave the ratio at 10 (ES points per SPY dollar) or adjust it.
  4. Read the approximate SPY open reference and the gap in dollars.
SPY reference = SPY close + (ES move in points ÷ ratio)
Example. SPY closed at 550.00. ES is up 25 points overnight. With a ratio of 10, the gap is 25 ÷ 10 = +2.50, so the reference is 552.50.

About this calculator

The S&P 500 index trades at roughly ten times the price of SPY, which is why ES points divided by about ten approximate SPY dollars. The ratio is not fixed: it drifts with futures basis, dividends and time to expiry, so treat the output as a reference, not a quote. The actual opening print also depends on the cash-open auction.

Frequently asked questions

How do I estimate where SPY will open from ES?
Take the overnight ES move in points, divide it by roughly 10 (the approximate ES-to-SPY ratio), and add the result to the prior SPY close. The calculator does this for you.
Is the result where SPY will open?
No. It is an arithmetic reference. The actual open depends on the opening auction, news, and how futures basis differs from the ratio you used.
Why is the ratio about 10?
ES tracks the S&P 500 index, which is priced at about ten times SPY. The exact relationship changes slightly with dividends and futures carry.

Planning around the SPY open?

See SPY premarket levels: structure, key levels and catalysts in futures and SPY/QQQ terms, before the 9:30 ET open.

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Overnight gap contextES vs SPY
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Informational calculator for reference only. Outputs are arithmetic, not quotes, recommendations or trade signals. LiquidityLevels provides educational market commentary, not financial advice.