is exempt goods excluded from aggregate turnover in gst.

Not for GST applicability.

Only for tax liability of composition dealers, it is excluded.

I am asking in gst registration aspects

For calculation of  the aggregate turnover for registration purpose, it includes taxable as well as non-taxable supplies......

As per SECTION 2(6), Aggregate Turnover also includes the value of Exempt Supplies.

As per SECTION 2[6], "aggregate turnover" means the aggregate value of all taxable supplies [excluding the value of inward supplies on which tax is payable by a person on reverse charge basis], exempt supplies, exports of goods or services or both and inter-State supplies of persons having the same Permanent Account Number, to be computed on all India basis but excludes central tax, State tax, Union territory tax, integrated tax and cess.

But if you Supply only Exempted Goods or Services or both, then you are not liable for Registration under GST as per SECTION 23 [ PERSONS NOT LIABLE FOR REGISTRATION ].