LDL Calculator

Determines the low-density lipoprotein levels based on cholesterol blood test results (total, HDL cholesterol levels & triglycerides).

In the text below the form there is in depth information on the formulas used and on the implications of LDL levels.

The LDL calculator estimates the low-density lipoprotein values given the cholesterol blood tests (total & HDL cholesterol and triglycerides).

The tool uses two different formulas Friedewald and Iranian and accommodates measurements in both mg/dL and mmol/L.

The two formulas used, depending on measurement units (mg/dL or mmol/L) are:

■ The Friedewald formula: LDL = TC - HDL – TG / 5.0 (mg/dL) or 2.17 (mmol/L)

■ The Iranian study formula: LDL = TC / 1.19 + TG / 1.9 (mg/dL) or 0.81 (mmol/L) – HDL / 1.1 – 38 (mg/dL) or 0.98 (mmol/L).

Total Cholesterol (TC)
HDL Cholesterol
Triglycerides (TG)
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Total Cholesterol (TC)
HDL Cholesterol
Triglycerides (TG)

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Steps on how to print your input & results:

1. Fill in the calculator/tool with your values and/or your answer choices and press Calculate.

2. Then you can click on the Print button to open a PDF in a separate window with the inputs and results. You can further save the PDF or print it.

Please note that once you have closed the PDF you need to click on the Calculate button before you try opening it again, otherwise the input and/or results may not appear in the pdf.



Low-density lipoprotein (LDL) cholesterol is also known as the “bad cholesterol” as it increases the risk of atherosclerosis and heart disease. This is because this type of cholesterol has a tendency to deposit on the blood vessel walls.

Aside from the danger of arterial blockage, the cholesterol plaque formed can rupture and turn into a blood clot who can in turn lead to a heart attack.

There are two formulas that can be used to determine LDL levels, the Friedewald equation (1972) and the Iranian study formula (2008). The former is more often used when triglyceride levels are lower than average, as in the case of patients with a prolonged low carbohydrate diet.

The equations are described depending on the initial measurement units for cholesterol, HDL and triglyceride levels:

In case of the first tab "LDL in mg/dL":

■ Friedewald formula: LDL = TC - HDL – TG / 5.0 (mg/dL)

■ Iranian study formula: LDL = TC / 1.19 + TG / 1.9 – HDL / 1.1 – 38 (mg/dL)

For the second tab "LDL in mmol/L":

■ Friedewald equation: LDL = TC - HDL – TG / 2.17 (mmol/L)

■ Iranian study method: LDL = TC / 1.19 + TG / 0.81 – HDL / 1.1 – 0.98 (mmol/L)


LDL testing

LDL checks are recommended every five years in most patients and even more frequently in patients with a family history of hypercholesterolemia and heart disease.

The LDL testing belongs to a simple blood test that measures the total cholesterol, HDL, LDL and triglyceride levels.

Regular monitoring can ensure appropriate measures are taken by patients with high cholesterol and can reduce the risk of developing a heart disease.


Medical implications

Cholesterol is a steroid substance that contributes to the integrity of cell membranes and is a precursor to various hormones and to vitamin D.

It is taken from diet but also synthesized in the liver and can be found in the bloodstream, attached to carries called lipoproteins (because it is not soluble in blood).

LDL is the complex of cholesterol attached to low density proteins whilst the other type, HDL is cholesterol attached to high density protein.

There are two varieties, the low density one LDL (because the particles tend to be less dense) and the high density one HDL.

HDL, or the good cholesterol, helps remove LDL from arteries and back to the liver. Therefore, it is important to maintain high levels of HDL to protect against heart attack and stroke.

Whilst lifestyle changes such as a healthy diet and exercise can protect against high cholesterol, in patients diagnosed with it, medication (with statins, niacin, fibrates or bile acid sequestrants) is often required to reduce levels significantly.

An LDL cholesterol lowering diet should be low in saturated fat and with plenty of fiber whilst exercise may have an influence in the formation of HDL, the beneficial cholesterol.



1. National Heart, Lung, and Blood Institute, American College of Cardiology, and American Heart Association Endorse Report. (2004) Update on Cholesterol Guidelines: More-Intensive Treatment Options for Higher Risk Patients.

2. Lecerf JM, de Lorgeril M. Dietary cholesterol: from physiology to cardiovascular risk. Br J Nutr. 2011; 106 (1): 6–14.

3. National Health Service. (2014) High Cholesterol levels.

Specialty: Nutrition

Objective: Determination

Type: Calculator

No. Of Variables: 3

Article By: Denise Nedea

Published On: June 2, 2017

Last Checked: June 2, 2017

Next Review: June 2, 2023