How wide are the keys on a modern piano compared with keys on early harpsichords?

For stringed keyboard instruments, natural keys have historically been no more than one inch wide. The octave span on a modern piano is approximately 6 1/2 inches (16.5 centimeters), which is very similar to the dimensions found on Flemish and Italian harpsichords from the 16th to 18th centuries.1

In contrast, English keyboards of that era typically featured a slightly narrower octave span of 6 3/8 inches (16.2 centimeters). Furthermore, many French and German instruments from the 18th century utilized an even narrower span of 6 1/4 inches (15.9 centimeters), a design choice that allowed pianists with average-sized hands to more easily play intervals such as tenths.1