UserID	test	testID	testValue
162430	Height	5	77
162430	Waist circumference	9	41.00

SELECT
	UserId,
	MAX(CASE WHEN test = 'Height' THEN testValue END )/
	MAX(CASE WHEN test = 'Waist Circumference' THEN testValue END ) AS HeightToWaistRatio
FROM
	Tble
GROUP BY
	UserId;

Msg 8117, Level 16, State 1, Line 1
Operand data type varchar is invalid for divide operator.

SELECT
	UserId,
	MAX(CASE WHEN test = 'Height' THEN convert(float,testValue) END )/
	MAX(CASE WHEN test = 'Waist Circumference' THEN convert(float,testValue) END ) AS HeightToWaist
FROM
	excz_measurements  where testid in (5,9) and userid = 162430
GROUP BY
	UserId;

SELECT
	UserId,
	100.0*MAX(CASE WHEN test = 'Height' THEN CAST(testValue AS FLOAT) END )/
	MAX(CASE WHEN test = 'Waist Circumference' THEN CAST(testValue AS FLOAT) END ) AS HeightToWaistRatio
FROM
	Tble
GROUP BY
	UserId;