NSString extension that allows calculating the size of a string more like sizeWithFont:

NSString+sizeWithFont.h

//
//  NSString+sizeWithFont.h
//  UTNoteLabelView
//
//  Created by Christian Enevoldsen on 05/08/13.
//  Copyright (c) 2013 Utunity. All rights reserved.
//

#import <Foundation/Foundation.h>

@interface NSString (sizeWithFont)

- (CGSize)sizeOfStringWithFont:(UIFont*)font;
- (CGSize)sizeOfStringWithFont:(UIFont*)font constrainedToSize:(CGSize)size;
- (CGSize)sizeOfStringWithFont:(UIFont *)font constrainedToSize:(CGSize)size lineBreakMode:(NSLineBreakMode)lineBreakMode;

@end

NSString+sizeWithFont.m

//
//  NSString+sizeWithFont.m
//  UTNoteLabelView
//
//  Created by Christian Enevoldsen on 05/08/13.
//  Copyright (c) 2013 Utunity. All rights reserved.
//

#import "NSString+sizeWithFont.h"

@implementation NSString (sizeWithFont)

- (CGSize)sizeOfStringWithFont:(UIFont *)font {
    return [self sizeOfStringWithFont:font constrainedToSize:CGSizeMake(CGFLOAT_MAX, CGFLOAT_MAX)];
}

- (CGSize)sizeOfStringWithFont:(UIFont *)font constrainedToSize:(CGSize)size {
	return [self sizeOfStringWithFont:font constrainedToSize:size lineBreakMode:NSLineBreakByWordWrapping];
}

- (CGSize)sizeOfStringWithFont:(UIFont *)font constrainedToSize:(CGSize)size lineBreakMode:(NSLineBreakMode)lineBreakMode {
	NSTextStorage *textStorage = [[NSTextStorage alloc] initWithString:self];
	NSTextContainer *textContainer = [[NSTextContainer alloc] initWithSize:size];
	NSLayoutManager *layoutManager = [[NSLayoutManager alloc] init];
	[layoutManager addTextContainer:textContainer];
	[textStorage addLayoutManager:layoutManager];
	[textStorage addAttribute:NSFontAttributeName value:font range:NSMakeRange(0, self.length)];
	[textContainer setLineBreakMode:lineBreakMode];
	[textContainer setLineFragmentPadding:0.0];
	(void)[layoutManager glyphRangeForTextContainer:textContainer];
	return [layoutManager usedRectForTextContainer:textContainer].size;
}

@end