Text size may be too small or big for you on your iPhone or iPad. If you are using iOS 7, It is very easy to change the font size and keep the same font size across the device. iOS 7 has dynamic font sizes.
iOS 7 has Dynamic Type font size. Any app that supports Dynamic Type font, adjusts its font as per settings. Regular iOS apps like Notes, Reminders, Settings Screen etc support Dynamic Type font.
How to change Font size on iOS 7 for iPhone/iPad/iPod Touch
1. On your iOS device, Go to Settings > General > Text Size > Drag the slider to increase or decrease Text size. Thats it. All the apps that use this feature will display bigger or smaller text.
2. Adjusting above Text Size increases slightly. But It does not increase it too big. If you want bigger font size, Go to Settings > General > Accessibility > Larger Type > Turn on Larger Dynamic Type. You can drag the slider more for larger text sizes.
You can see the difference with larger text size in the above image.
3. To compare different text sizes, look at the sample notes in the Notes iOS app below.
Changed Text Size is reflected all core iOS apps including Phone app for Contact Names, Notes app, Reminders app etc.