LDL Calculator
Estimate LDL cholesterol from total cholesterol, HDL and triglycerides with the Friedewald and NIH equations.
About the LDL Calculator
Most labs calculate LDL rather than measure it. The classic Friedewald formula (1972) is LDL = total − HDL − triglycerides ÷ 5 in mg/dL; it underestimates LDL when LDL is low or triglycerides are high, and is invalid above 400 mg/dL. The NIH equation (Sampson et al., 2020) is more accurate across a wider range, up to 800 mg/dL of triglycerides, and many US labs now use it.
The formula
Friedewald: LDL = TC − HDL − TG ÷ 5; NIH: LDL = TC ÷ 0.948 − HDL ÷ 0.971 − (TG ÷ 8.56 + TG × non-HDL ÷ 2140 − TG² ÷ 16100) − 9.44
Worked example
Example: LDL (NIH / Sampson equation) = 145 mg/dL
- Inputs: Units: mg/dL; Total cholesterol: 230; HDL cholesterol: 55; Triglycerides: 170.
- Formula: Friedewald: LDL = TC − HDL − TG ÷ 5; NIH: LDL = TC ÷ 0.948 − HDL ÷ 0.971 − (TG ÷ 8.56 + TG × non-HDL ÷ 2140 − TG² ÷ 16100) − 9.44
- Result: LDL (NIH / Sampson equation) = 145 mg/dL
- LDL, NIH equation: 145 mg/dL
- LDL, Friedewald: 141 mg/dL
- Non-HDL cholesterol: 175 mg/dL
Questions people ask
Do I need to fast?
Not usually for these equations, but very high triglycerides after a meal reduce accuracy.
Which LDL target applies to me?
It depends on your heart risk; your doctor sets it.