Pianos are very heavy. Most spinet or console pianos weigh approximately three hundred to five hundred pounds, old uprights at about seven hundred, and sometimes close to a thousand pounds. Grand pianos average from about five hundred to a thousand pounds, though some concert grands can weigh more than a thousand pounds!
If it were a matter of weight, all it would take would be enough strong people to do the job of lifting and loading. Unfortunately, with the weight comes problems of balance and inertia. Experience makes the moving of your piano safe and efficient. Most professional movers use two or three people who are of average size if they have, experience, the right equipment, and know when and where to lift. The shape, fragile cabinet, inner mechanism and the uneven weight distribution demands the proper equipment, but also an understanding of the balance and inertia that pianos pose.
Trying to move a piano by yourself may easily result in damage to both you and your piano.