Some code to look at how much accuracy a double has

double.cfm

<cfscript>
  struct function compareStringToNumeric(string s){
		var result = {
			asString	= s,
			asNumber	= val(s)
		};
		result.equal = !compare(result.asString, result.asNumber);
		return result;
	}

	integerOnly = "";
	decimalOnly = "";
	withBoth	= "";
	intPart		= "";
	decPart		= "";
	xls = spreadsheetNew();
</cfscript>

<table border="1">
	<tr>
		<th rowspan="2">Digits</th>
		<th colspan="3">Integer</th><th colspan="3">Decimal</th><th colspan="3">Both</th>
	</tr>
	<tr>
		<th>String</th><th>Number</th><th>Equal</th>
		<th>String</th><th>Number</th><th>Equal</th>
		<th>String</th><th>Number</th><th>Equal</th>
	</tr>
	<cfloop index="i" from="1" to="20">
		<cfif i mod 10>	<!---omit zeros as they will be ignored if trailing--->
			<cfscript>
				integerOnly &= (i mod 10);
				decimalOnly = "0.#integerOnly#";
				if (i mod 2){
					intPart &= (i mod 10);
				}else{
					decPart &= (i mod 10);
				}
				withBoth ="#len(intPart)?intPart:0#.#len(decPart)?decPart:0#";	// make sure the decimal point is handled the same as the numeric will be (leading & trailing zero if necessary)

				intCompared = compareStringToNumeric(integerOnly);
				decCompared = compareStringToNumeric(decimalOnly);
				withBothCompared = compareStringToNumeric(withBoth);
			</cfscript>
			<cfoutput>
			<tr>
				<td>#i#</td>
				<td>#integerOnly#</td>
				<td>#intCompared.asNumber#</td>
				<td>#intCompared.equal#</td>
				<td>#decimalOnly#</td>
				<td>#decCompared.asNumber#</td>
				<td>#decCompared.equal#</td>
				<td>#withBoth#</td>
				<td>#withBothCompared.asNumber#</td>
				<td>#withBothCompared.equal#</td>
			</tr>
			</cfoutput>
			<cfscript>
				spreadsheetSetCellValue(xls, i, i, 1);

				spreadsheetSetCellValue(xls, integerOnly, i, 2);
				spreadsheetSetCellValue(xls, intCompared.asNumber, i, 3);
				spreadsheetSetCellFormula(xls, "if(B#i#=C#i#,true, false)", i, 4);

				spreadsheetSetCellValue(xls, decimalOnly, i, 5);
				spreadsheetSetCellValue(xls, decCompared.asNumber, i, 6);
				spreadsheetSetCellFormula(xls, "if(E#i#=F#i#,true, false)", i, 4);

				spreadsheetSetCellValue(xls, withBoth, i, 8);
				spreadsheetSetCellValue(xls, withBothCompared.asNumber, i, 9);
				spreadsheetSetCellFormula(xls, "if(H#i#=I#i#,true, false)", i, 4);
			</cfscript>
		</cfif>
	</cfloop>
</table>
<cfset spreadsheetWrite(xls, expandPath("./") & "result.xls", true)>