Help Galaxy S3 battery drains faster while closing to die.

[Hasan Sameeh]

I have Samsung Galaxy 3, and I've been having a problem that the battery starts running out faster when it kinda reaches 35%
and it gets faster when it's 20%
and when it's 10% I only can start running looking for the charger, it lasts like 30 minutes of using after 30%.

does anyone know what is that problem about and how can I solve it ?
it's literally killing me :/

 

[Hadron]

The rate of power consumption won't increase as the battery discharges, so this can only mean that the calibration is inaccurate.

An obvious question though: is this the original battery? This could possibly be a symptom of battery ageing.