The range of a Nadex spread can vary based on how far a particular underlying market’s price can move in a given time period, and how long it is until the spread’s expiration. With longer durations, the spread range will be wider between floor and ceiling. The shorter durations have narrower ranges.
The reason for this is straightforward: the more time a market has to move around, the further it may move. So Nadex gives a wider range to a spread that will have more time to move around.
For example the Nadex US500 spread, based on the CME E-mini S&P Futures, typically has ranges like these:
Daily – The US500 1990.0- 2030.0 spread has a strike width of 40.0 points, equivalent to a $400 range value. The daily spread’s duration is from the prior evening to the expiration at 4:15pm ET, or 22 hours 15 minutes.
Daily – The US500 2000.0 -2030.0 spread has a strike width of 30.0 points, equivalent to a $300 range value. The shorter daily spread’s duration is from 8am to 4:15pm ET, or 8 hours, 15 minutes.
2hour- The US500 2020.0 - 2030.0 spread has a strike width of 10.0 points, equivalent to a $100 range value. The 2-hour spreads are listed every hour, beginning at 8am, and have hourly expirations from 10am until 4pm ET. In other words, a new spread is listed every hour and each one lasts for two hours, with the last one running from 2pm to 4pm ET.