これを試して、
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
// add your code snippet here
// dynamically change the label height,
       CGSize textSize = {
        200.0,   // limit width
        20000.0  // and height of text area
    };
    CGSize contentSize = [yourText sizeWithFont:[UIFont systemFontOfSize:15.0] constrainedToSize:textSize lineBreakMode:NSLineBreakByWordWrapping];
    CGFloat contentHeight = contentSize.height < 36? 36: contentSize.height; // lower bound for height
    CGRect labelFrame = [yourLabel frame];
    yourLabel.size.height = contentHeight;
    [yourLabel setFrame: labelFrame];
    [yourLabel setText:yourText];
    return cell;
}
セルの高さを動的に変更し、
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
    YourCell *currentCell = (YourCell*)[self tableView:tableView cellForRowAtIndexPath:indexPath];
// change hard coded value based on your cell alignment
    int cellLength=[currentCell.yourLabel.text length]/42;
    cellLength = cellLength*22 > 200 ? cellLength*22 : 200;
    CGSize constraint = CGSizeMake((200 - 10), cellLength);
    CGSize size1 = [cellText sizeWithFont:[UIFont systemFontOfSize:15] constrainedToSize:constraint lineBreakMode:NSLineBreakByWordWrapping];
    return 220+size1.height;
}