Quickstart notes
A decimal-to-American formula for your odds sheet
One IF formula converts the decimal columns to American odds in place, with the two guards that keep blank rows and the 2.00 pivot right.
The sheet does its job in decimal prices, because that is what the feed serves. Then someone asks for the American version, and the answer is one formula, not another column of typing. Here is the formula, where it goes, and the two details that make it trustworthy.
The formula, once
American odds split at 2.00. At or above it, the American number is the decimal minus one, times 100. Below it, it is minus 100 divided by the decimal minus one. In a sheet cell, with the decimal price in E2:
=IF(E2>=2, ROUND((E2-1)*100), ROUND(-100/(E2-1)))ROUND to whole numbers keeps the display conventional: +150, not +150.4. Drop the ROUND if you want the raw figure for further math; the integer form is for eyes.
The Sheets quickstart writes decimal prices into columns E to G, checked 2026-11-06, so the American versions live in the three columns right of them, each formula pointing at its decimal neighbor.
Put it next to the refresh, not in it
The tempting move is converting inside the Apps Script, writing both formats on every run. The better move is a formula column that reads the decimal cells: the script stays untouched, the refresh stays fast, and the conversion re-evaluates for free whenever the sheet recalculates.
That separation also protects the history tab. If you log prices, log them in decimal, the format the feed served, and let the display layer convert. A stored American price is a decimal price with a translation glued on, and every later computation has to peel the glue off first.
The two edge cases worth a note
Decimal 2.00 is the pivot: the formula returns +100 there, even money, exactly as it should. The failure to guard is the cell below 1.00 or empty, which divides by zero or worse. Wrap it: =IF(NOT(ISNUMBER(E2)),"",IF(E2<=1,"",...)) keeps blank rows and bad reads quiet instead of loud.
The second detail is sign expectations. Readers used to American prices expect a plus on the underdogs and a minus on the favorites; the formula produces both from the same decimal cell without you thinking about it, because the split at 2.00 is built in.
What the sheet gains
A decimal board for your records, an American column for whoever reads it, and zero extra calls to the feed. The conversion is arithmetic the sheet does locally, so the cadence and the quota never notice.
One formula, three columns, no new fetch. The sheet now speaks both formats, and the decimal row underneath stays the one of record.