Cm² to hectares
One square centimetre is 1.000000e-08 hectares, and this shows the working rather than just the answer. Nothing you type here leaves your browser — it is worked out on your own device, so there is nothing to send and nothing to log.
The factor
One square centimetre is 1.000000e-08 hectares. That is the whole of the conversion: multiply by it, and nothing else happens.
And it is exact
Not rounded, not measured, not a convention that might be revised. The factor above is the definition, so an answer from it is as exact as the number you typed.
The hectare is 10,000 m², or a square 100 m on a side.
There is no shorter version
The factor is short enough to use as it stands, so nobody carries a rounded one and there is nothing to get wrong.
Going the other way
The reverse is not this sum backwards in your head. It is a different factor, 100,000,000, and dividing by one is not the same as multiplying by a rounded version of the other.
Rounded, the way back is 99,999,999.999999985099, which is low by 1.490116e-14%. So the two roundings do not cancel: go out and back with both and you do not land where you started.
How many of those decimals mean anything
The box above will give you ten decimal places because it can. Whether they mean anything is decided by your measurement, not by the arithmetic.
If you measured to the nearest square centimetre, your figure is already uncertain by half of one — so the answer is uncertain by about 5.000000e-09 hectares, and every digit past that is decoration. Quoting 1.234560e-08 when you measured with a tape is claiming a precision the tape never had.
Where these two sit
Cm² and hectares both measure area, which is why they can be converted at all. A conversion between families — a length into a weight — is not a conversion, it is a question with a missing quantity in it.
The unit converter pairs cm² with in² rather than with hectares, because that is the conversion people ask for most. This page exists because a good many ask for this one instead.
Other conversions from cm²
m² · ft² · in² · km² · acres · yd²