A modern U.S. dollar bill measures approximately 6.14 × 2.61 inches, or 15.60 × 6.63 cm. Those are its long and short edges.
Modern U.S. notes of different denominations share this face size. A $100 bill is not larger than a $1 or $20 bill.
The U.S. Currency Education Program's history describes the standardized small-note format as 6.14 × 2.61 inches. The figures below convert those listed dimensions; they are reference values, not a precision measurement of every individual note.