Estimate LDL cholesterol from a standard lipid panel using the Friedewald equation. All values in mg/dL. Not valid if triglycerides exceed 400 mg/dL. For educational use only.
Formula (Friedewald): LDL = Total Cholesterol - HDL - (Triglycerides / 5). Not valid when triglycerides > 400 mg/dL. Source: Friedewald et al., Clin Chem 1972.
This is an estimate, not a direct measurement. Only a healthcare provider can interpret your cholesterol values in clinical context.
Most standard lipid panels in the United States report an estimated LDL cholesterol calculated from the Friedewald equation rather than a direct measurement. This calculator performs that same calculation using values from a lipid panel.
For example: Total cholesterol 200, HDL 55, Triglycerides 150. LDL = 200 - 55 - (150 / 5) = 200 - 55 - 30 = 115 mg/dL.
The equation was published by Friedewald WT, Levy RI, and Fredrickson DS in Clinical Chemistry in 1972: "Estimation of the Concentration of Low-Density Lipoprotein Cholesterol in Plasma, Without Use of the Preparative Ultracentrifuge." Reference: Clin Chem. 1972;18(6):499-502. See PubMed: Friedewald et al. 1972.
The Friedewald equation must not be used when triglycerides exceed 400 mg/dL. The equation assumes that VLDL cholesterol equals triglycerides divided by 5, which holds reasonably well at normal triglyceride levels. Above 400 mg/dL, this ratio breaks down and the equation underestimates LDL. Direct LDL measurement by ultracentrifugation or beta-quantification is required in those cases.
The equation is also unreliable in type III hyperlipoproteinemia (familial dysbetalipoproteinemia), where VLDL particle composition differs. Your laboratory report will note whether direct or estimated LDL was used.
| LDL (mg/dL) | Category (NHLBI) |
|---|---|
| Below 100 | Optimal |
| 100 to 129 | Near optimal / above optimal |
| 130 to 159 | Borderline high |
| 160 to 189 | High |
| 190 and above | Very high |
These are general reference ranges from the National Heart, Lung, and Blood Institute. Individual LDL targets vary by cardiovascular risk factors, age, sex, and personal history. A healthcare provider sets the appropriate target for each patient.
See also: BMI Calculator using the CDC formula, and Body Surface Area (BSA) Calculator using the Mosteller formula.
The Friedewald equation estimates LDL cholesterol as: LDL = Total Cholesterol - HDL - (Triglycerides / 5), where all values are in mg/dL. It was published by Friedewald, Levy, and Fredrickson in Clinical Chemistry in 1972. This equation is the basis for most routine lipid panel LDL estimates in the United States.
The Friedewald equation is not valid when triglycerides are greater than 400 mg/dL. At high triglyceride levels, the ratio of triglycerides to VLDL changes and the equation underestimates LDL. It is also not accurate in type III hyperlipoproteinemia. Direct LDL measurement should be used in these cases.
General reference ranges from the NHLBI: below 100 mg/dL is optimal, 100 to 129 mg/dL is near optimal, 130 to 159 mg/dL is borderline high, 160 to 189 mg/dL is high, and 190 mg/dL or above is very high. Optimal LDL targets vary by individual cardiovascular risk and should be discussed with a healthcare provider.
Dividing triglycerides by 5 estimates the VLDL cholesterol fraction (in mg/dL). Total cholesterol equals LDL plus HDL plus VLDL. Rearranging gives LDL = Total Cholesterol - HDL - VLDL, and the equation substitutes triglycerides / 5 as an approximation of VLDL.
No. This calculator requires measured lipid panel values from a blood test as inputs. It cannot replace a blood test. The result is an estimate, not a direct measurement. Only a healthcare provider can interpret your cholesterol values in clinical context.