The average tension of a string on a modern piano is 165 pounds. Spread over the whole piano, the tension on the strings is about 18 tons. A grand piano can average over 20 tons of tension.*
In related news, there’s such a thing as a boudoir or parlor grand piano. It’s the middle child of the grand family, falling between the concert and baby grands. I have never played one.**
**Woe is me (or, if I have, I’ve never known it).