LDL Cholesterol Calculator (Friedewald, Martin-Hopkins, Sampson)

Q: Which LDL equation is most accurate?

Martin-Hopkins and Sampson both out-perform Friedewald, especially when triglycerides are above 150 mg/dL or LDL is below 70 mg/dL, where Friedewald under-estimates LDL and can wrongly suggest a target has been met. The 2018 ACC/AHA guideline mentions Martin-Hopkins for low LDL; Sampson is accurate to higher triglyceride levels. For a routine panel with normal triglycerides the three agree within a few mg/dL.

Q: Why does Friedewald stop working at triglycerides of 400 mg/dL?

Because the fixed TG ÷ 5 estimate of VLDL cholesterol breaks down as triglyceride-rich remnant particles accumulate: the subtraction becomes too large and the LDL estimate too low, sometimes negative. Laboratories do not report a Friedewald LDL above 400 mg/dL (4.5 mmol/L); use Martin-Hopkins (valid to about 800) or Sampson, or ask for a direct LDL measurement.

Q: What is non-HDL cholesterol and why is it shown?

Total cholesterol minus HDL: the cholesterol in all the atherogenic particles (LDL, VLDL, remnants, lipoprotein(a)). It needs no equation, is valid when triglycerides are high and after a meal, and guidelines set targets for it 30 mg/dL (0.8 mmol/L) above the LDL target.

Q: Do I need to fast for this calculation?

A fasting sample reduces triglycerides and so changes the subtraction. Guidelines now accept non-fasting panels for screening, but if triglycerides are above 400 mg/dL on a non-fasting sample the LDL should be repeated fasting or measured directly. Martin-Hopkins and Sampson are less affected by a non-fasting rise.

Q: How do I convert LDL between mg/dL and mmol/L?

Divide mg/dL by 38.67 to get mmol/L (100 mg/dL = 2.59 mmol/L) and multiply mmol/L by 38.67 to get mg/dL. Triglycerides use 88.57 instead (150 mg/dL = 1.69 mmol/L) because the molecule is heavier. The tile "LDL in the other unit" does this for the result.

Q: What LDL level should I aim for?

It depends on risk, not on the LDL alone. Under 100 mg/dL is optimal for most adults; people with established cardiovascular disease or diabetes are usually treated to below 70 mg/dL (1.8 mmol/L), and the 2019 ESC/EAS guideline goes to below 55 mg/dL (1.4 mmol/L) at very high risk. An LDL of 190 mg/dL or more warrants evaluation for familial hypercholesterolaemia. Discuss the target with your clinician.

Calculate LDL cholesterol from total cholesterol, HDL and triglycerides with the Friedewald equation, the Martin-Hopkins 180-cell factor table or the Sampson (NIH) equation, in mg/dL or mmol/L, with non-HDL cholesterol.

Last updated: October 2026

Units

Total cholesterol

HDL cholesterol

Triglycerides

Equation

LDL cholesterol

120 mg/dL

This calculator gives an estimate for general information only. It is not medical advice and does not replace a doctor, pharmacist or other qualified health professional. Always check with them before acting on the result, especially for medication doses, children, pregnancy or a medical condition, and follow the guidelines of your local health authority.

Formula below · 4 sources (nhlbi.nih.gov, medlineplus.gov, pmc.ncbi.nlm.nih.gov, doi.org) · Updated Oct 2026

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About this calculator

Most laboratories do not measure LDL cholesterol directly. They measure total cholesterol (TC), HDL cholesterol and triglycerides (TG), and estimate LDL as what is left after HDL and the cholesterol carried in VLDL particles are subtracted. The three equations differ only in how they estimate the VLDL cholesterol.

Friedewald (1972). LDL = TC − HDL − TG ÷ 5 in mg/dL (TG ÷ 2.2 in mmol/L). It assumes the TG-to-VLDL-cholesterol ratio is always 5. It is simple and still the most common, but it under-estimates LDL when triglycerides are high or LDL is low (below about 70 mg/dL), and it is invalid at triglycerides of 400 mg/dL (4.5 mmol/L) or more, where the calculator refuses to use it.

Martin-Hopkins (2013). LDL = non-HDL − TG ÷ factor, where non-HDL = TC − HDL and the factor is read from a 180-cell table (30 triglyceride strata × 6 non-HDL strata) of median TG:VLDL-C ratios derived from 1.35 million lipid profiles measured by ultracentrifugation. The factor runs from 3.1 to 11.9: higher triglycerides and lower non-HDL mean a larger factor and so a smaller VLDL subtraction. This calculator holds the full published table and shows the factor it used. The 2018 ACC/AHA cholesterol guideline names it as a reasonable alternative to Friedewald when LDL is below 70 mg/dL.

Sampson / NIH equation 2 (2020). LDL = TC ÷ 0.948 − HDL ÷ 0.971 − (TG ÷ 8.56 + TG × non-HDL ÷ 2140 − TG² ÷ 16100) − 9.44, in mg/dL. A closed-form equation fitted to beta-quantification results that stays accurate up to triglycerides of about 800 mg/dL and at low LDL.

Units. In mmol/L the calculator converts cholesterol values by 38.67 and triglycerides by 88.57 to mg/dL, applies the equations, and converts the answer back. Non-HDL cholesterol (TC − HDL) is shown as a tile because it needs no equation and is a treatment target in its own right.

The result is an estimate of a laboratory value for information; lipid treatment decisions rest on the full risk picture and a clinician's advice.

Martin-Hopkins adjustable factor (TG ÷ VLDL-C): selected triglyceride rows of the 180-cell table, by non-HDL cholesterol (mg/dL)

Scroll sideways to see all columns →

Triglycerides (mg/dL)	Non-HDL <100	100-129	130-159	160-189	190-219	≥220
7-49	3.5	3.4	3.3	3.3	3.2	3.1
80-83	5	4.8	4.6	4.4	4.3	4.2
101-105	5.5	5.2	5	4.7	4.6	4.5
147-154	6.5	6	5.7	5.4	5.1	4.8
202-220	7.6	6.9	6.4	6	5.6	5.3
293-399	9.5	8.3	7.5	7	6.5	5.9
400-13,975	11.9	10	8.8	8.1	7.5	6.7

Source: Martin SS et al. JAMA 2013 (supplementary eTable); the calculator holds all 30 rows

How to use

Enter the three values from the same lipid panel, in the units printed on it, and pick the equation (the tiles always show all three). Example (the defaults): total cholesterol 200, HDL 50, triglycerides 150 mg/dL. Friedewald: 200 − 50 − 150 ÷ 5 = 120 mg/dL. Non-HDL = 150 mg/dL. Martin-Hopkins: triglycerides 150 fall in the 147-154 row and non-HDL 150 in the 130-159 column, factor 5.7, so LDL = 150 − 150 ÷ 5.7 = 150 − 26.3 = 123.7 mg/dL. Sampson: 200 ÷ 0.948 − 50 ÷ 0.971 − (150 ÷ 8.56 + 150 × 150 ÷ 2140 − 150² ÷ 16100) − 9.44 = 210.97 − 51.49 − (17.52 + 10.51 − 1.40) − 9.44 = 123.4 mg/dL. Example with high triglycerides, in mmol/L: total cholesterol 5.2, HDL 1.0, triglycerides 3.4 mmol/L (201, 39 and 301 mg/dL). Friedewald gives 5.2 − 1.0 − 3.4 ÷ 2.2 = 2.65 mmol/L (102 mg/dL). Martin-Hopkins uses the 293-399 row and the 160-189 non-HDL column (non-HDL = 162 mg/dL), factor 7.0: 162 − 301 ÷ 7.0 = 119 mg/dL = 3.08 mmol/L, 17 mg/dL higher than Friedewald, which is the typical direction of the Friedewald error when triglycerides are high.

Frequently asked questions

Which LDL equation is most accurate?

Martin-Hopkins and Sampson both out-perform Friedewald, especially when triglycerides are above 150 mg/dL or LDL is below 70 mg/dL, where Friedewald under-estimates LDL and can wrongly suggest a target has been met. The 2018 ACC/AHA guideline mentions Martin-Hopkins for low LDL; Sampson is accurate to higher triglyceride levels. For a routine panel with normal triglycerides the three agree within a few mg/dL.

Why does Friedewald stop working at triglycerides of 400 mg/dL?

Because the fixed TG ÷ 5 estimate of VLDL cholesterol breaks down as triglyceride-rich remnant particles accumulate: the subtraction becomes too large and the LDL estimate too low, sometimes negative. Laboratories do not report a Friedewald LDL above 400 mg/dL (4.5 mmol/L); use Martin-Hopkins (valid to about 800) or Sampson, or ask for a direct LDL measurement.

What is non-HDL cholesterol and why is it shown?

Total cholesterol minus HDL: the cholesterol in all the atherogenic particles (LDL, VLDL, remnants, lipoprotein(a)). It needs no equation, is valid when triglycerides are high and after a meal, and guidelines set targets for it 30 mg/dL (0.8 mmol/L) above the LDL target.

Do I need to fast for this calculation?

A fasting sample reduces triglycerides and so changes the subtraction. Guidelines now accept non-fasting panels for screening, but if triglycerides are above 400 mg/dL on a non-fasting sample the LDL should be repeated fasting or measured directly. Martin-Hopkins and Sampson are less affected by a non-fasting rise.

How do I convert LDL between mg/dL and mmol/L?

Divide mg/dL by 38.67 to get mmol/L (100 mg/dL = 2.59 mmol/L) and multiply mmol/L by 38.67 to get mg/dL. Triglycerides use 88.57 instead (150 mg/dL = 1.69 mmol/L) because the molecule is heavier. The tile "LDL in the other unit" does this for the result.

What LDL level should I aim for?

It depends on risk, not on the LDL alone. Under 100 mg/dL is optimal for most adults; people with established cardiovascular disease or diabetes are usually treated to below 70 mg/dL (1.8 mmol/L), and the 2019 ESC/EAS guideline goes to below 55 mg/dL (1.4 mmol/L) at very high risk. An LDL of 190 mg/dL or more warrants evaluation for familial hypercholesterolaemia. Discuss the target with your clinician.

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