As near as damn it/dammit
Definition 1 of 1
Pro Tip 1/3British Colloquialism
This phrase is mostly used in the UK and might not be understood in other English-speaking regions. 
Overseas, you might not hear 'as near as damn it' often, but in Britain, it's common.
Pro Tip 2/3Informal Tone
The phrase is informal, so it's not suitable for formal writing or speeches. 
In an academic essay, avoid saying 'The results were as near as damn it accurate.'
Pro Tip 3/3Exaggerated Precision
Used to express that something is practically precise, while acknowledging a tiny margin of error. 
He guessed the weight as near as damn it—it was only off by an ounce.