LDL Cholesterol Calculator — Friedewald Formula
Calculator
LDL Cholesterol Calculator
Calculate LDL with the Friedewald formula from total cholesterol, HDL and triglycerides, with non-HDL cholesterol, TC/HDL ratio and target by risk category
The calculator applies the Friedewald formula (LDL = total cholesterol − HDL − triglycerides/5 in mg/dL, /2.2 in mmol/L), which is not valid with triglycerides above 400 mg/dL (4.5 mmol/L), and shows the 2020 Sampson/NIH equation for comparison. The LDL targets are those of the ESC/EAS guidelines on dyslipidaemias. It is an informational tool: your cardiovascular risk category is determined by your doctor, and the calculation does not replace the laboratory report or a clinical assessment. For the interpretation of your tests, consult your doctor.
More Details
How the LDL cholesterol calculator works
In short: the LDL calculation with the Friedewald formula is LDL = total cholesterol − HDL − triglycerides ÷ 5, with all values in mg/dL. With total 220, HDL 50 and triglycerides 150: 220 − 50 − 30 = 140 mg/dL. The formula only applies with triglycerides up to 400 mg/dL; above that, direct measurement in the laboratory is needed.
LDL cholesterol is the cholesterol fraction that cardiology guidelines use as the main target of prevention: the higher it is and the longer it stays high, the greater the risk of atherosclerotic cardiovascular disease. In most Italian lab reports LDL is not measured directly but calculated from three lipid profile values: total cholesterol, HDL cholesterol and triglycerides. This free calculator performs the same calculation with the Friedewald formula, and adds non-HDL cholesterol, the total/HDL ratio and a comparison with the LDL target for your risk category. Everything happens in your browser: the values you enter are not sent to any server.
You can work in mg/dL, the unit almost always used in Italian lab reports, or in mmol/L, common in other European countries: the calculator adjusts the formula, thresholds and targets accordingly.
The Friedewald formula and its limits
The formula proposed by Friedewald, Levy and Fredrickson in 1972 estimates LDL by subtracting the HDL and VLDL fractions from total cholesterol, the latter approximated as one fifth of triglycerides:
| Unit | Formula | Estimated VLDL cholesterol |
|---|---|---|
| mg/dL | LDL = total − HDL − triglycerides / 5 | triglycerides / 5 |
| mmol/L | LDL = total − HDL − triglycerides / 2.2 | triglycerides / 2.2 |
The fixed divisor is also the weak point of the formula: it assumes that the ratio between triglycerides and cholesterol in VLDL is constant, which stops being true when triglycerides rise. For this reason the formula cannot be applied with triglycerides above 400 mg/dL (4.5 mmol/L): above that threshold it underestimates LDL and direct laboratory measurement is needed. In that case the calculator shows an error rather than a number. The estimate is also less precise with very low LDL, and the blood sample should normally be taken while fasting.
For comparison, the calculator shows a second line with the Sampson/NIH equation, published in 2020 in JAMA Cardiology and now adopted by several laboratories in place of Friedewald: it replaces the fixed divisor with a term that depends on both triglycerides and non-HDL cholesterol, remains valid up to 800 mg/dL of triglycerides and is more accurate when LDL is low. The two estimates may differ by a few mg/dL: this is normal, and it serves as a reminder that calculated LDL is precisely an estimate.
Calculation example
A report with total cholesterol 220 mg/dL, HDL 50 mg/dL and triglycerides 150 mg/dL, in a person at moderate cardiovascular risk:
| Item | Calculation | Result |
|---|---|---|
| Estimated VLDL cholesterol | 150 / 5 | 30 mg/dL |
| LDL cholesterol (Friedewald) | 220 − 50 − 30 | 140 mg/dL |
| Non-HDL cholesterol | 220 − 50 | 170 mg/dL |
| Total / HDL ratio | 220 / 50 | 4.4 |
| LDL with the Sampson/NIH equation | full equation | 143.1 mg/dL |
| LDL target at moderate risk | < 100 mg/dL | 40 mg/dL above the target |
The same values in mmol/L (5.70 total, 1.30 HDL, 1.70 triglycerides) give an LDL of 3.63 mmol/L: the small difference compared with the direct conversion of 140 mg/dL is due to the fact that the 2.2 divisor of the formula in SI units is itself a rounded figure.
Quick examples in mg/dL
| Total | HDL | Triglycerides | Calculated LDL | Working |
|---|---|---|---|---|
| 200 | 60 | 100 | 120 mg/dL | 200 − 60 − 20 |
| 180 | 55 | 90 | 107 mg/dL | 180 − 55 − 18 |
| 250 | 45 | 200 | 165 mg/dL | 250 − 45 − 40 |
| 240 | 40 | 450 | cannot be calculated | triglycerides above 400: direct measurement needed |
If your report already shows an LDL value, check whether it is “calculated” or “direct”: the direct one is measured in the laboratory, the calculated one is an estimate like the one on this page.
Non-HDL cholesterol and total/HDL ratio
Non-HDL cholesterol (total minus HDL) includes all potentially atherogenic lipoproteins, not just LDL, and has the advantage of not being affected by the limits of the Friedewald formula: it can still be calculated with high triglycerides and does not require fasting. European guidelines indicate it as a secondary target. The total cholesterol / HDL ratio, on the other hand, is a summary index: a lower value is more favourable, but on its own it does not define a person's risk.
LDL targets by risk category
The 2019 ESC/EAS guidelines on dyslipidaemias — whose targets were confirmed in the 2025 Focused Update — set different LDL thresholds based on the person's cardiovascular risk:
| Risk category | LDL target | Notes |
|---|---|---|
| Very high | < 55 mg/dL (1.4 mmol/L) | and a reduction of at least 50% from the baseline value |
| High | < 70 mg/dL (1.8 mmol/L) | and a reduction of at least 50% from the baseline value |
| Moderate | < 100 mg/dL (2.6 mmol/L) | target to be considered |
| Low | < 116 mg/dL (3.0 mmol/L) | target that may be considered |
This is the most important point of the whole tool: you do not choose the risk category yourself, and this page does not calculate it. It is determined by your doctor, who assesses your medical history, previous cardiovascular events, diabetes, kidney function, familial hypercholesterolaemia and risk charts such as SCORE2. If it has never been communicated to you, leave the “I don't know” option selected: the calculator will show all targets without assigning one to you.
When this calculation is not enough
This is an informational tool. It does not replace the laboratory report, which remains the reference document, nor the assessment of your doctor, who is the only one able to interpret the values in the context of your medical history and to decide whether and how to intervene. In particular, a clinical assessment is needed when triglycerides exceed 400 mg/dL, when a familial form is suspected, when values change a lot from one test to the next, or when you are already taking lipid-lowering medication. No value calculated on a web page is a reason to start, change or stop a treatment.
Frequently asked questions
How is LDL cholesterol calculated with the Friedewald formula?
HDL cholesterol and one fifth of triglycerides are subtracted from total cholesterol: LDL = total − HDL − triglycerides/5, with values in mg/dL. In mmol/L the triglyceride divisor becomes 2.2. With total 220, HDL 50 and triglycerides 150 mg/dL, the calculated LDL is 140 mg/dL.
Why doesn't the formula work with high triglycerides?
Because the fixed divisor assumes a constant ratio between triglycerides and cholesterol in VLDL, which does not hold when triglycerides increase. Above 400 mg/dL (4.5 mmol/L) the Friedewald formula is not considered valid and underestimates LDL: in that case direct laboratory measurement of LDL cholesterol is needed.
What is the ideal LDL cholesterol value?
There is no single value: it depends on the cardiovascular risk category. According to the ESC/EAS guidelines, the target is below 55 mg/dL at very high risk, 70 mg/dL at high risk, 100 mg/dL at moderate risk and 116 mg/dL at low risk. The category is determined by the doctor, not by the calculator.
What is the difference between LDL cholesterol and non-HDL cholesterol?
Non-HDL cholesterol is simply total minus HDL and includes all atherogenic lipoproteins, LDL included. It is useful because it does not depend on the limits of the Friedewald formula and remains reliable even with high triglycerides or without fasting; European guidelines use it as a secondary target alongside LDL.
Related tools: the body mass index (BMI) calculator, the glomerular filtration rate (GFR) calculator and the calorie calculator.
