Double field size in MS Access
In MS Access both double and long integer are number types and they both differ from each other. Double can hold values of floating point number to decimal precision of 15 and it has the storage capacity of about 8 bytes.
Whereas long integer hold only integer and also holds floating point number by converting them automatically to integer. The memory of integer is less than double that is 4 bytes.
For example if you store this number 12345.123 in double it will store it as it is, but in long integer it will restore it as 12345 and leave the floating point number.