# tonumber(e [, base])

Tries to convert its argument to a number. If the argument is already a number or a string convertible to a number, then `tonumber`

returns this number; otherwise, it returns **null**.

An optional argument specifies the base to interpret the numeral. The base may be any integer between 2 and 36, inclusive. In bases above 10, the letter '`A`

' (in either upper or lower case) represents 10, '`B`

' represents 11, and so forth, with '`Z`

' representing 35. In base 10 (the default), the number can have a decimal part, as well as an optional exponent part (see Values and Types). In other bases, only unsigned integers are accepted.