About the LDL Cholesterol Calculator
This LDL cholesterol calculator estimates your low-density lipoprotein (“bad”) cholesterol from the three values measured directly on a standard lipid panel: total cholesterol, HDL and triglycerides. Most labs do not measure LDL directly — they calculate it — so this lets you check the figure on your report, compare methods, or estimate LDL from older results.
Two equations are shown. The classic Friedewald formula (1972) is simple and still widely used, but it underestimates LDL when triglycerides are high or LDL is low, and is invalid at triglycerides of 400 mg/dL or more. The NIH equation published by Sampson and colleagues in 2020 is more accurate across a wider range and remains usable up to 800 mg/dL triglycerides; it is increasingly adopted by US labs.
Enter results in mg/dL or mmol/L. The category uses the NCEP ATP III LDL bands. Your treatment target depends on your overall cardiovascular risk, so discuss results with a clinician rather than acting on LDL alone.
With the default inputs, the ldl cholesterol (your units) is 120. Change any value above to recalculate instantly.
How to use the ldl cholesterol calculator
- 1Choose mg/dL or mmol/L to match your lab report.
- 2Enter total cholesterol, HDL cholesterol and triglycerides.
- 3Pick Friedewald or the NIH equation as the headline method.
- 4Compare both estimates and read your LDL category.
Formula and method
Friedewald assumes VLDL cholesterol is one-fifth of triglycerides (in mg/dL), so LDL is whatever cholesterol is left after subtracting HDL and VLDL from the total. That fixed ratio breaks down when triglycerides are high, which is why the formula is not used at 400 mg/dL or more.
The NIH equation (Sampson et al., JAMA Cardiology 2020) was fitted against ultracentrifugation reference measurements and adds a non-linear triglyceride term, making it more accurate for high triglycerides and low LDL. The Martin-Hopkins method takes a different approach, dividing TG by a factor looked up from a 180-cell table. mmol/L values are converted with 38.67 (cholesterol) and 88.57 (triglycerides).
- TC
- Total cholesterol, mg/dL
- HDL
- HDL cholesterol, mg/dL
- TG
- Triglycerides, mg/dL
- NonHDL
- TC − HDL
Worked examples
Typical panel: TC 200, HDL 50, TG 150 mg/dL
Friedewald: 200 − 50 − 150 ÷ 5 = 120 mg/dL. The NIH equation gives about 123 mg/dL. Both are in the near-optimal band of 100–129 mg/dL.
High triglycerides: TC 240, HDL 38, TG 450 mg/dL
With triglycerides at 450, Friedewald (240 − 38 − 90 = 112) is invalid and underestimates LDL. The NIH equation gives about 122 mg/dL and is used as the headline figure.
mmol/L panel: TC 5.5, HDL 1.3, TG 1.7
Converted to mg/dL, TG ÷ 5 is 30.1, so LDL = 212.7 − 50.3 − 30.1 = 132.3 mg/dL, or about 3.42 mmol/L (the mmol/L shortcut TC − HDL − TG ÷ 2.2 gives 3.43). That is borderline high.
Frequently asked questions
What is a normal LDL cholesterol level?+
For most adults, LDL below 100 mg/dL (2.6 mmol/L) is considered optimal and 100–129 near optimal. 130–159 is borderline high, 160–189 high and 190 mg/dL (4.9 mmol/L) or more very high. People with heart disease or diabetes often aim lower.
How is LDL calculated from a lipid panel?+
Most labs use the Friedewald formula: LDL = total cholesterol − HDL − triglycerides ÷ 5 (in mg/dL). In mmol/L, divide triglycerides by 2.2 instead of 5. Some labs now use the NIH or Martin-Hopkins equations.
When is the Friedewald formula not accurate?+
It becomes unreliable when triglycerides are above about 400 mg/dL (4.5 mmol/L), after a non-fasting meal with high fat, when LDL is very low (below about 70 mg/dL), and in some lipid disorders. Newer equations or a direct LDL test are better then.
What about the Martin-Hopkins LDL calculation?+
Martin-Hopkins replaces the fixed “÷ 5” with one of 180 factors chosen from a table by triglyceride and non-HDL levels. It performs similarly to the NIH equation shown here; both are more accurate than Friedewald at low LDL and high triglycerides.
Do I need to fast before a cholesterol test?+
Fasting is often no longer required for routine lipid testing. Non-fasting triglycerides are slightly higher, which lowers Friedewald LDL a little; if triglycerides come back high, a fasting repeat may be requested.
This tool gives general estimates and is not medical advice. Talk to a doctor or qualified professional about your health, diet or training.