Why dose my nikon d5300 battery drain when the camera is turned off?

Why dose my nikon d5300 battery drain when the camera is turned off?

Your camera draws 250 microamps maximum (from the Nikon service manuals for the D40, D50 and D90) when the power switch is in the Off position AND the internal clock/memory battery is fully charged. The internal battery is not accessible by the user. It also draws 250 microamps max when the power switch is in the On position and the camera is in sleep mode. The power switch on Nikon DSLRs is a "soft" power switch. They do it so the internal memory buffer can be properly cleared when you turn the camera off (you can still be writing to memory after the power switch is turned off which is more likely to happen if shooting raw or you just took a mess of shots in continuous mode). You'll notice that when your camera power is off, whenever you insert or remove the memory card, the memory card busy light will flash.

250 uA is not much current. On a full charge, your camera battery will last about 1 year if the camera is turned off. If your battery is show significant drain in 1 month of not being used, you have a problem (bad body or battery).

There are certain functions that keep working when the camera is off, such as the clock. The clock keeps time so that when you turn the camera back on, it has the correct time.

If the camera is sitting unused for months, draining of the batteries in it would be normal. If it is draining in only a few weeks or days, something may be wrong.

Along with all the reasons given by others, the batteries themselves will lose some capacity due to self-discharge. The lithium ion batteries commonly used in batteries don't drain as quickly as other types rechargeables, but should still be topped off every month or so, and should be removed from the camera when left unused for any length of time.