Cholesterol Ratio Calculator

Cholesterol ratios provide a more nuanced picture of cardiovascular risk than any single cholesterol number. The two most clinically useful ratios are the Total Cholesterol to HDL ratio and the LDL to HDL ratio.

Formulas:

Total Cholesterol to HDL Ratio: TC/HDL = Total Cholesterol ÷ HDL Cholesterol

LDL to HDL Ratio: LDL/HDL = LDL Cholesterol ÷ HDL Cholesterol

Calculated LDL (the Friedewald equation, used when LDL is not measured directly): LDL = Total Cholesterol − HDL − (Triglycerides ÷ 5) (valid only when triglycerides are under 400 mg/dL)

Leave the LDL box empty and this calculator fills it in for you with Friedewald, provided you have entered triglycerides. Above 400 mg/dL of triglycerides the equation breaks down and it will say so instead of guessing, because the “divide by 5” step is an assumption about VLDL composition that stops holding at high triglyceride levels.

Non-HDL Cholesterol (includes all atherogenic particles): Non-HDL = Total Cholesterol − HDL

What each variable means:

• Total Cholesterol (TC): sum of all cholesterol types in your blood.
• HDL: “good” cholesterol; higher is better; removes cholesterol from arteries.
• LDL: “bad” cholesterol; deposits in artery walls; lower is better.
• Triglycerides: a type of fat in the blood; elevated by sugar and alcohol intake.

Reference ranges (mg/dL):

Worked example: Blood panel: TC = 210, HDL = 58, Triglycerides = 120, LDL not measured. LDL = 210 − 58 − (120 ÷ 5) = 210 − 58 − 24 = 128 TC/HDL = 210 ÷ 58 = 3.62 (acceptable) LDL/HDL = 128 ÷ 58 = 2.21 (acceptable)

Enter those three numbers with the LDL box left blank and the calculator reproduces all of it.

Why the ratio can move without your cholesterol changing. Both halves are levers, and HDL is the one people forget. Someone with a total of 210 and HDL of 42 has a ratio of exactly 5.0. Raise HDL to 60 and the ratio drops to 3.5 with the total untouched. That is why a doctor may be relaxed about a total cholesterol figure that looks alarming on its own, and unhappy about one that looks fine.

Note: Ratios summarise a lipid panel, they do not replace a full cardiovascular risk assessment. Age, blood pressure, smoking and diabetes all sit outside these numbers.