sizeWithFont method is deprecated. Replace with sizeWithAttributes.

Create category that works for both iOS7 and iOS8 or only use sizeWithAttributes.

#import "NSString+StringSizeWithFont.h"

@implementation NSString (StringSizeWithFont)

- (CGSize) sizeWithMyFont:(UIFont *)fontToUse

{

    if ([self respondsToSelector:@selector(sizeWithAttributes:)])

    {

        NSDictionary* attribs = @{NSFontAttributeName:fontToUse};

        return ([self sizeWithAttributes:attribs]);

    }

    return ([self sizeWithFont:fontToUse]);

}

@end

Category call :

    NSString *text= @"Do any additional setup after loading the view, typically from a nib.";

    CGSize fontSize = [text sizeWithMyFont:[UIFont fontWithName:@"Helvetica"

                                                         size:12]];

    

    NSLog(@"Calculate Size with sizeWithAttributes : %f %f", fontSize.height, fontSize.width);

    

    CGSize fontSize1 = [text sizeWithFont:[UIFont fontWithName:@"Helvetica"

                                                           size:12]];

    

    NSLog(@"Calculate Size with sizeWithFont: %f %f", fontSize1.height, fontSize1.width);

OutPut :

015-01-12 11:10:47.348 DemoTest[1149:38359] Calculate Size with sizeWithAttributes : 13.800000 350.871094

2015-01-12 11:10:47.349 DemoTest[1149:38359] Calculate Size with sizeWithFont: 14.000000 351.000000