sizeWithFont method is deprecated. boundingRectWithSize returns an unexpected value

How about create new label and using sizeThatFit:(CGSize)size ??

UILabel *gettingSizeLabel = [[UILabel alloc] init];
gettingSizeLabel.font = [UIFont fontWithName:@"YOUR FONT's NAME" size:16];
gettingSizeLabel.text = @"YOUR LABEL's TEXT";
gettingSizeLabel.numberOfLines = 0;
gettingSizeLabel.lineBreakMode = NSLineBreakByWordWrapping;
CGSize maximumLabelSize = CGSizeMake(310, CGFLOAT_MAX);

CGSize expectSize = [gettingSizeLabel sizeThatFits:maximumLabelSize];

Edit: This upper code is not good for ios 7 and above, so please use below:

CGRect textRect = [myString boundingRectWithSize:maximumLabelSize   
                         options:NSStringDrawingUsesLineFragmentOrigin| NSStringDrawingUsesFontLeading
                         attributes:@{NSFontAttributeName:fontText}
                         context:nil];

Maybe you need to provide additional option to the method that is suggested in this answer:

CGSize maximumLabelSize = CGSizeMake(310, CGFLOAT_MAX);
CGRect textRect = [myString boundingRectWithSize:maximumLabelSize   
                                         options:(NSStringDrawingUsesLineFragmentOrigin|NSStringDrawingUsesFontLeading)
                                      attributes:@{NSFontAttributeName: fontText}
                                         context:nil];

Here is my working code snippet:

NSMutableDictionary *dict = [NSMutableDictionary dictionaryWithDictionary:attributeDict];

NSString *headline  = [dict objectForKey:@"title"];  
UIFont *font        = [UIFont boldSystemFontOfSize:18];  
CGRect  rect        = [headline boundingRectWithSize:CGSizeMake(300, 1000) options:NSStringDrawingUsesLineFragmentOrigin|NSStringDrawingUsesFontLeading attributes:@{NSFontAttributeName:font} context:nil];

CGFloat height      = roundf(rect.size.height +4)

I added 4px to the calculated height, because without these 4px, there is one line missing.

I use this code snippet in a tableView and add the "height" to an array of NSNumbers and I get the correct cell height for the default textLabel.

Add 4 more pixel if you want more space under the text in the textLabel.

**** UPDATE ****

I do not agree with the "width bug of 40px", I shout be the 4px of missing height, because 4px is the default height of a space between a letter and the bound of a single line. You can check it with a UILabel, for a fontsize of 16 you need a UILabel height of 20.

But if your last line has no "g" or whatever in it, the measuring could be miss the 4px of height.

I rechecked it with a little method, I get an accurate height of 20,40 or 60 for my label and a right width less than 300px.

To support iOS6 and iOS7, you can use my method:

- (CGFloat)heightFromString:(NSString*)text withFont:(UIFont*)font constraintToWidth:(CGFloat)width
{
    CGRect rect;

    float iosVersion = [[[UIDevice currentDevice] systemVersion] floatValue];
    if (iosVersion >= 7.0) {
        rect = [text boundingRectWithSize:CGSizeMake(width, 1000) options:NSStringDrawingUsesLineFragmentOrigin|NSStringDrawingUsesFontLeading attributes:@{NSFontAttributeName:font} context:nil];
    }
    else {
        CGSize size = [text sizeWithFont:font constrainedToSize:CGSizeMake(width, 1000) lineBreakMode:NSLineBreakByWordWrapping];
        rect = CGRectMake(0, 0, size.width, size.height);
    }
    NSLog(@"%@: W: %.f, H: %.f", self, rect.size.width, rect.size.height);
    return rect.size.height;
}

**** UPGRADE ****

Thanks to your comments, I upgraded my function as followed. Since sizeWithFont is deprecated and you will get a warning in XCode, I added the diagnostic-pragma-code to remove the warning for this particular function-call/block of code.

- (CGFloat)heightFromStringWithFont:(UIFont*)font constraintToWidth:(CGFloat)width
{
    CGRect rect;

    if ([self respondsToSelector:@selector(boundingRectWithSize:options:attributes:context:)]) {
        rect = [self boundingRectWithSize:CGSizeMake(width, 1000) options:NSStringDrawingUsesLineFragmentOrigin|NSStringDrawingUsesFontLeading attributes:@{NSFontAttributeName:font} context:nil];
    }
    else {
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
        CGSize size = [self sizeWithFont:font constrainedToSize:CGSizeMake(width, 1000) lineBreakMode:NSLineBreakByWordWrapping];
        rect = CGRectMake(0, 0, size.width, size.height);
#pragma GCC diagnostic pop
    }
    return ceil(rect.size.height);
}

In addition to the 4px topic: depending which font and font-weight you use, the calculation returns different height-values. In my case: HelveticaNeue-Medium with a fontsize of 16.0 returns a line-height of 20.0 for a single line but 39.0 for two lines, 78px for 4 lines --> 1px missing for every line - beginning with line 2 - but you want to have your fontsize + 4px linespace for every line you have to get a height-result.
Please keep that in mind while coding!
I don´t have a function yet for this "problem" but I will update this post when I´m finished.