LDL Calculator
Work out calculated LDL cholesterol from a standard lipid panel with the NIH Sampson and Friedewald equations side by side, plus non-HDL and ATP III range.
LDL Calculator: with the default inputs, calculated ldl cholesterol is 123.4.
Use whatever your lab report uses. All three values must be in the same unit.
Sampson stays accurate at higher triglycerides. Both are always shown below.
In the unit you entered, from the equation you chose.
- ATP III LDL category
- Near or above optimal (100–129 mg/dL)
- Sampson / NIH LDL
- 123.4
- Friedewald LDL
Not reported when triglycerides are 400 mg/dL (4.5 mmol/L) or higher.
- 120
- Non-HDL cholesterol
Total minus HDL. ATP III sets non-HDL goals 30 mg/dL above the LDL goal.
- 150
- In words
- Sampson LDL is 123 mg/dL, which ATP III classes as near or above optimal. Non-HDL cholesterol is 150 mg/dL.
Assumptions
- This is an estimate for education. It does not diagnose anything and does not replace your clinician or a measured LDL.
- Both equations are applied in mg/dL. mmol/L inputs are converted at 38.67 mg/dL per mmol/L for cholesterol and 88.57 for triglycerides.
- Friedewald is not reported at triglycerides of 400 mg/dL or more; Sampson is not reported above 800 mg/dL.
- Categories are the NCEP ATP III LDL classes (NHLBI, 2002). Current guidelines base treatment on overall risk rather than these classes alone.
| Equation | LDL (mg/dL) | ATP III category | Valid for |
|---|---|---|---|
| Sampson / NIH (2020) | 123 | Near or above optimal | TG up to 800 mg/dL (9.0 mmol/L) |
| Friedewald (1972) | 120 | Near or above optimal | TG below 400 mg/dL (4.5 mmol/L) |
| LDL (mg/dL) | Category | Total cholesterol (mg/dL) |
|---|---|---|
| 100 | Near or above optimal from here | 176 |
| 130 | Borderline high from here | 207 |
| 160 | High from here | 237 |
| 190 | Very high from here | 268 |
ATP III LDL categories (NHLBI, 2002). Holding HDL and triglycerides at your values.
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How this is worked out
The formula
Sampson / NIH (mg/dL): LDL = TC/0.948 − HDL/0.971 − (TG/8.56 + TG × NonHDL/2140 − TG²/16100) − 9.44 Friedewald (mg/dL): LDL = TC − HDL − TG/5 (not valid when TG ≥ 400 mg/dL) Non-HDL = TC − HDL TC = total cholesterol, HDL = HDL cholesterol, TG = triglycerides, all in mg/dL mmol/L → mg/dL: cholesterol × 38.67, triglycerides × 88.57
Open How it’s calculated above to see this worked through with your own numbers.
What you enter
- Units
- Use whatever your lab report uses. All three values must be in the same unit.mg/dL (US) · mmol/L
- Total cholesterol
- A number.from 0 to 1500 · defaults to 200
- HDL cholesterol
- A number.from 0 to 300 · defaults to 50
- Triglycerides
- A number.from 0 to 5000 · defaults to 150
- Equation
- Sampson stays accurate at higher triglycerides. Both are always shown below.Sampson / NIH (2020) · Friedewald (1972)
What you get back
- Calculated LDL cholesterolmain answer
- In the unit you entered, from the equation you chose.
- ATP III LDL category
- Sampson / NIH LDL
- Friedewald LDL
- Not reported when triglycerides are 400 mg/dL (4.5 mmol/L) or higher.
- Non-HDL cholesterol
- Total minus HDL. ATP III sets non-HDL goals 30 mg/dL above the LDL goal.
- In words
What this assumes
- This is an estimate for education. It does not diagnose anything and does not replace your clinician or a measured LDL.
- Both equations are applied in mg/dL. mmol/L inputs are converted at 38.67 mg/dL per mmol/L for cholesterol and 88.57 for triglycerides.
- Friedewald is not reported at triglycerides of 400 mg/dL or more; Sampson is not reported above 800 mg/dL.
- Categories are the NCEP ATP III LDL classes (NHLBI, 2002). Current guidelines base treatment on overall risk rather than these classes alone.
About this calculator
Most lipid panels do not measure LDL cholesterol at all. They measure total cholesterol, HDL and triglycerides, then calculate LDL from those three numbers — which is why your report may say "LDL, calculated". This calculator reproduces that step with the two equations labs use, so you can check a result, see how much the choice of equation matters for your numbers, or estimate LDL from an older report that left it out.
The two equations
Friedewald (1972) is the classic: LDL = total cholesterol − HDL − triglycerides ÷ 5, in mg/dL. The ÷ 5 is an estimate of the cholesterol carried in VLDL particles. It works reasonably at normal triglycerides but under-estimates LDL as triglycerides rise, and it is not used at all once triglycerides reach 400 mg/dL.
Sampson / NIH (2020), published in JAMA Cardiology by researchers at the National Institutes of Health, replaces the fixed ÷ 5 with terms that change with triglyceride and non-HDL levels. It was fitted against ultracentrifugation, the reference method, and stays accurate up to triglycerides of 800 mg/dL. A growing number of labs now report it, and it is the default here.
How to use it
Enter total cholesterol, HDL and triglycerides from the same panel and pick mg/dL or mmol/L to match your report. The headline uses the equation you choose; the table underneath always shows both, with the ATP III category for each. The calculator also gives non-HDL cholesterol (total minus HDL), which counts every atherogenic particle and does not need a fasting sample.
Reading the result
The NCEP ATP III categories for LDL are: under 100 mg/dL optimal, 100–129 near or above optimal, 130–159 borderline high, 160–189 high and 190 or higher very high. The chart plots your total cholesterol against your triglycerides, with each category boundary drawn at your HDL, so you can see how far you are from the next band. The second table gives the total cholesterol at which you would cross each threshold.
Treatment decisions today rest on overall cardiovascular risk, not on an LDL category alone — the ASCVD risk calculator is the tool for that conversation.
Caveats
Both equations are estimates. Non-fasting samples raise triglycerides and can shift calculated LDL by several points. At very high triglycerides, or when an LDL result will drive a treatment change near a target, ask for a directly measured LDL. Mixing units — mmol/L entered as mg/dL — is the commonest error, and the calculator flags values that look like the wrong unit.
Frequently asked questions
▸What does "LDL calculated" mean on my lab report?
The lab measured total cholesterol, HDL and triglycerides and worked LDL out from them with an equation, usually Friedewald or the newer Sampson/NIH equation. A directly measured LDL is labelled "direct LDL".
▸Which is more accurate, Friedewald or Sampson?
Sampson. In the 2020 NIH study it matched ultracentrifugation more closely than Friedewald, especially at triglycerides of 150–800 mg/dL and at low LDL, where Friedewald under-estimates.
▸Why can't Friedewald be used when triglycerides are over 400?
Friedewald assumes VLDL cholesterol is one fifth of triglycerides. Above 400 mg/dL that ratio breaks down badly, so labs either use Sampson or measure LDL directly.
▸What is a good non-HDL cholesterol?
ATP III sets non-HDL goals 30 mg/dL above the LDL goal, so under 130 mg/dL corresponds to an LDL goal under 100. Your own target depends on your overall cardiovascular risk.
▸How do I convert cholesterol from mmol/L to mg/dL?
Multiply total, HDL and LDL cholesterol by 38.67. Triglycerides use a different factor: multiply by 88.57.
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