149 in Roman numerals

How CXLIX is built

Roman numerals are written one decimal place at a time, largest first.

1. Chundreds · 1C is 100.
2. XLtens · 4X before L means 50 − 10 = 40. This saves writing XXXX.
3. IXones · 9I before X means 10 − 1 = 9. This saves writing VIIII.

100 + 40 + 9 = 149

The pairs XL and IX use subtraction: a smaller letter before a larger one is taken away from it. Only six pairs work this way: IV, IX, XL, XC, CD and CM. More on subtraction

Mistakes to avoid

• Not CIL. It looks like a shortcut, but I may only come before V or X, not L. The correct form is CXLIX.
• Not CXXXXVIIII (10 letters). That adds everything up without subtraction. The Romans sometimes wrote numbers this way, and clocks still show 4 as IIII, but today CXLIX (5 letters) is the standard.