LDL cholesterol calculator
Enter total cholesterol, HDL and triglycerides from a lipid panel to estimate LDL ("bad") cholesterol with the Friedewald and the Sampson/NIH equations, in mg/dL or mmol/L. It is an estimate for information, not a diagnosis.
Runs in your browser: nothing you enter is sent anywhere.
How to use it
- Pick the units on your lab report: mg/dL or mmol/L.
- Enter total cholesterol, HDL cholesterol and triglycerides.
- Read LDL by both equations and non-HDL cholesterol. A line under the results says which equations apply to your triglyceride level.
All values in mg/dL (TC total cholesterol, HDL, TG triglycerides):
- Friedewald: LDL = TC − HDL − TG / 5. Not used when TG is 400 mg/dL or more.
- Sampson (NIH equation 2): LDL = TC / 0.948 − HDL / 0.971 − (TG / 8.56 + TG × non-HDL / 2140 − TG² / 16100) − 9.44, where non-HDL = TC − HDL. Used up to TG 800 mg/dL.
For mmol/L the inputs are converted to mg/dL (× 38.67 for cholesterol, × 88.57 for triglycerides) and the result is divided by 38.67. The Friedewald term then equals TG / 2.18 in mmol/L, close to the TG / 2.2 often quoted.
Worked example
Total cholesterol 200, HDL 50, triglycerides 150 mg/dL:
- Friedewald: 200 − 50 − 150 / 5 = 120 mg/dL.
- Sampson: 200 / 0.948 = 210.97; 50 / 0.971 = 51.49; the triglyceride term is 17.52 + 10.51 − 1.40 = 26.64; 210.97 − 51.49 − 26.64 − 9.44 = 123 mg/dL.
- Non-HDL: 200 − 50 = 150 mg/dL.
Tips
- Use values from the same blood sample: mixing results from different days skews the estimate.
- With very high triglycerides ask for a direct LDL measurement instead of a calculated one.
- LDL targets depend on your overall cardiovascular risk; the ASCVD risk calculator estimates that risk for adults 40 to 79.
- This is an estimate for information, not a diagnosis or a treatment decision.
Frequently asked questions
Which LDL equation is more accurate?
Friedewald is the classic one and works well when triglycerides are normal. The Sampson (NIH) equation from 2020 was built to stay closer to measured LDL when triglycerides are high or LDL is low, and it can be used up to 800 mg/dL of triglycerides. The two give similar numbers on a typical panel.
Why is there no Martin–Hopkins result?
The Martin–Hopkins method divides triglycerides by a factor read from a 180-cell table. This calculator only uses formulas it can reproduce exactly, so it gives Friedewald and Sampson; many labs report one of these or a direct LDL.
Do I need to fast before the test?
Non-fasting panels are widely used. Triglycerides rise after a meal, and a higher triglyceride value lowers a calculated LDL a little. If your triglycerides were high, ask whether a fasting repeat is needed.
What is non-HDL cholesterol?
Total cholesterol minus HDL: all the cholesterol carried by particles that can build up in arteries. It needs no equation and is valid at any triglyceride level.
How do I convert mmol/L to mg/dL?
Multiply cholesterol by 38.67 and triglycerides by 88.57. The calculator converts mmol/L values this way before applying the equations and converts LDL back.