LDL Friedewald Calculator
The formula
What the friedewald ldl tells you
The 1972 subtraction that made LDL a routine lab value without ultracentrifugation — total minus HDL minus estimated VLDL.
Calculation: LDL = TC − HDL − TG/5 (valid when TG <400). Enter your inputs and every substitution is shown below the result.
Reading the result
Where LDL and non-HDL disagree, non-HDL is the more honest target in hypertriglyceridemia.
Rules of thumb: Guideline targets from <100 (diabetes) to <70 or <55 mg/dL (very-high-risk ASCVD)
Limitations and best practice
TG/5 fails when triglycerides are high or in type III dysbetalipoproteinemia — calculated LDL can come out negative or absurd.
This calculator gives an estimate based on standard formulas; it is not professional financial, medical, legal or engineering advice. Verify anything you plan to act on with a qualified professional and your own records.
Frequently asked questions
Do I need to fast for Friedewald?
Why are labs moving to direct LDL?
Source & methodology
Friedewald Clin Chem 1972.
LDL Friedewald explained: formula, worked example and honest limits
You are here because you need a specific number, and you want to see how it was produced before you rely on it. There are plenty of pages about LDL Friedewald; almost none of them show the working. This one does: the formula, every input, a fully computed example, and a sensitivity analysis calculated live from this engine’s own defaults.
It helps to separate the mechanics from the interpretation. The mechanics are fixed: LDL = TC − HDL − TG/5 (valid when TG <400). Anyone, anywhere, entering the same inputs will get the same 104 mg/dL. The interpretation is where experience counts: whether 104 mg/dL is good, normal or alarming depends on comparisons covered below, and that is the part most articles about LDL Friedewald never explain.
People rarely disagree about arithmetic; they disagree about assumptions that were never written down. Printing the substitution and the sensitivity ranking removes that category of disagreement for LDL Friedewald.
What makes a calculation page trustworthy is that its copy is derived from its own arithmetic: here calculated LDL = 104 mg/dL, recomputed every time a field changes, and the sensitivity section ranks the inputs that move the result — Total cholesterol first, at ≈17.8 % of the headline for a ten-percent error either way in that input. Work down the page and by the end you could re-derive the result in a spreadsheet from memory.
Inside the LDL Friedewald calculation: formula and every input
Here is the complete model this tool runs — LDL = TC − HDL − TG/5 (valid when TG <400) — with each input explained below. If a competitor’s page gives you a different answer from the same inputs, this is the text that settles which of you is right.
Total cholesterol (mg/dL) (example value 185) is a numeric input whose unit is fixed by the label; a wrong unit is a wrong answer wearing a plausible disguise. Figures of this kind carry safety consequences; when in doubt, use the conservative value and confirm with a professional.
HDL (mg/dL) (example value 51) is a quantity rather than a category — precision here is cheap and worth having. Figures of this kind carry safety consequences; when in doubt, use the conservative value and confirm with a professional.
Triglycerides (mg/dL) (example value 150) is a quantity rather than a category — precision here is cheap and worth having. Figures of this kind carry safety consequences; when in doubt, use the conservative value and confirm with a professional.
A fully worked LDL Friedewald example
The tool prints its own working; this is the same arithmetic on the example values, reproduced so you can follow it by hand. Starting figures: Total cholesterol (mg/dL), HDL (mg/dL), Triglycerides (mg/dL). Run to the end, the calculated LDL resolves to 104 mg/dL — Friedewald LDL 104 mg/dL from 150 TG assumes VLDL = TG/5 — the estimate degrades as TG rise on the bands this tool uses.
- VLDL ≈ 150 ÷ 5 = 30
- LDL = 185 − 51 − 30 = 104
- Below 400 TG the formula is ±~5–10 mg/dL; above it, it is not a number
Non-HDL cholesterol — 134 mg/dL. Compare it against the main result of 104 mg/dL before drawing conclusions.
VLDL estimate — 30 mg/dL. If your inputs change, this is usually the first companion figure to move.
Validity — TG <400 — usable. If your inputs change, this is usually the first companion figure to move.
Remnant cholesterol — 30 mg/dL. If your inputs change, this is usually the first companion figure to move.
Keep this worked example open while you enter your own figures: matching the shape of the substitution is the fastest way to spot a unit or convention mistake.
Scenario table: LDL Friedewald at ±10 % and ±20 % of the key input
Single-point answers invite false confidence, so the same engine was run across a band around the input that matters most here. Each row is a full recalculation of LDL Friedewald, not an interpolation.
| Total cholesterol setting | Calculated LDL |
|---|---|
| 80 % of the example value | 67 mg/dL |
| 90 % of the example value | 86 mg/dL |
| example inputs | 104 mg/dL |
| 110 % of the example value | 123 mg/dL |
| 120 % of the example value | 141 mg/dL |
The corridor runs from 67 mg/dL to 141 mg/dL across that band — which is the range worth planning inside rather than the single 104 mg/dL point estimate. Reproduce it in the form above by editing Total cholesterol alone; the substitution steps will follow your figures exactly.
What actually moves your LDL Friedewald
This list was computed for this specific engine just now: each numeric input was nudged ±10 % while every other field held its example value, and the calculated LDL was recalculated from scratch. Read it as a map of where LDL Friedewald is fragile — drawn for the example inputs, which is the map you want when deciding what to measure carefully.
- Total cholesterol +10 % → LDL Friedewald = 123 mg/dL · −10 % → 86 mg/dL (the calculated LDL shifts ≈17.8 %)
- HDL: ten percent up gives 99 mg/dL, ten percent down gives 109 mg/dL — ≈4.9 % of the calculated LDL either way
- Nudge Triglycerides by ±10 % and LDL Friedewald lands between 101 mg/dL and 107 mg/dL (sensitivity ≈2.9 %)
Total cholesterol is the dominant lever here: ten percent either way moves the result by about 17.8 %, from 86 mg/dL to 123 mg/dL. Measure that input from a document rather than from memory, and treat HDL as the second priority (≈4.9 % per ten percent). Everything below that can stay approximate, which is a licence to stop chasing data that would not change the decision.
Is your LDL Friedewald good — reading the result bands
The value above only becomes useful the moment you know what it is being measured against. On the example inputs the band reads “Friedewald LDL 104 mg/dL from 150 TG assumes VLDL = TG/5 — the estimate degrades as TG rise”; your own figures place you on a different rung of the same ladder. How much of that band is luck? On Total cholesterol alone ten percent either way covers 86 mg/dL to 123 mg/dL. The practical reading rules: compare against your own history before comparing against other people; treat band boundaries as zones, not walls — one point on the wrong side of a threshold rarely changes a real outcome; and when a companion output contradicts the headline, believe the pair.
Where LDL Friedewald sits next to similar measures: this tool answers “how much is the LDL Friedewald”, while the related calculators answer “what do I do about it”. Reading the result alone tends to over-weight a single snapshot; pairing it with the companion tools above turns the number into a decision.
The errors that quietly break an LDL Friedewald figure
TG/5 fails when triglycerides are high or in type III dysbetalipoproteinemia — calculated LDL can come out negative or absurd. This calculator gives an estimate based on standard formulas; it is not professional financial, medical, legal or engineering advice. Verify anything you plan to act on with a qualified professional and your own records.
Treating the example inputs as a recommendation. They are a demonstration of the mechanism — a decision-grade LDL Friedewald begins the moment your own figures replace them.
This model has its own particular trap: Total cholesterol carries ≈17.8 % of the response per ten percent of error, so effort spent elsewhere is largely decorative.
The subtlest error is answering the wrong question precisely. Confirm that calculated LDL is actually the quantity your decision needs — the arithmetic is flawless either way, which is what makes the mistake invisible.
A quick check for any LDL Friedewald figure
- Compare the result with one independent method or published benchmark.
- Confirm the example values are plausible for your own situation before replacing them.
- Re-verify Total cholesterol against a source document — ten percent of error there moves the headline by ≈17.8 %.
- Re-run the calculation with a ±10 % stress on the two most sensitive inputs.
- Note the date and the inputs beside the number so the figure can be audited later.
- Confirm the answer against one independent method or published benchmark for LDL Friedewald.
Step by step: getting a trustworthy LDL Friedewald out of this tool
The tool does the arithmetic; the routine below is what makes the arithmetic trustworthy. Five steps, a minute total — and afterwards you will know not just what the number is, but which assumption produced it.
Step 1 — start from evidence. The inputs behind LDL Friedewald are total cholesterol (mg/dl), hdl (mg/dl), triglycerides (mg/dl). Write them down with their source next to each one; if you cannot name where a figure came from, that is the input most likely to be wrong. Estimates improve most when the worst case is written down in ink.
Step 2 — baseline before exploration. Get one defensible Calculated LDL on screen before you start nudging numbers. Without a baseline, every variation looks interesting and none of them means anything. Write the assumptions in the same file as the result, and future arguments take minutes instead of meetings.
Step 3 — isolate your variables. Change one field, observe, revert. The live sensitivity list does the ranking for the default inputs; verify it against your own, because dominance shifts when the starting point shifts. Write the figure down before moving on; memory flatters whichever number you saw last.
Step 4 — stress before you commit. A decision that survives a ten-percent squeeze on its two biggest inputs needs no luck to be sound. One that does not survive is a decision about hope, not about arithmetic. If the answer changes your behaviour, it deserves a second run with different assumptions.
Step 5 — write the one-line memo. “Calculated LDL = 104 mg/dL on this date, from these inputs.” That line is the entire deliverable; everything else on this page is how you earned the right to write it. Note the assumption you are least sure about; that is where the real risk lives.
Where LDL Friedewald matters in practice
Health & Medical arguments end at arithmetic or they do not end. LDL Friedewald is the arithmetic: 104 mg/dL on the example inputs, reproducible by anyone who types the same numbers. Precision is a promise you make about your data; make sure your inputs can keep it.
Used properly this is a five-minute filter that saves weeks. Compute LDL Friedewald, reject what fails, and only then bring in the expensive analysis for the survivors. One decimal place more than your data supports is one decimal place of fiction.
Treat LDL Friedewald like a smoke alarm rather than a painting — its value is in being tested periodically, not in being admired once. Re-running a number costs seconds; retracting a decision costs considerably more.
People also ask about LDL Friedewald
What affects LDL Friedewald the most?
LDL Friedewald is driven above all by Total cholesterol. Perturbing only that field by ten percent either way produced 123 mg/dL against the 104 mg/dL baseline — a ≈17.8 % response, while HDL manages ≈4.9 %.
Which matters more: hdl or total cholesterol?
For LDL Friedewald, Total cholesterol wins the head-to-head (≈17.8 % against ≈4.9 % per ten-percent change). Knowing which input dominates is the difference between careful work and merely slow work.
What is a typical LDL Friedewald?
There is no honest universal average for LDL Friedewald, but there is a reference point: the defaults on this page produce 104 mg/dL (Friedewald LDL 104 mg/dL from 150 TG assumes VLDL = TG/5 — the estimate degrades as TG rise). Replace the inputs with your own and compare — that comparison is the useful meaning of “typical”.
How do I calculate LDL Friedewald by hand?
LDL = TC − HDL − TG/5 (valid when TG <400) is the entire method. Work the inputs in that order — VLDL ≈ 150 ÷ 5 = 30 — and you will reach 104 mg/dL on the default figures, the same number this tool prints.
What happens to LDL Friedewald if total cholesterol changes by 10 %?
The engine was re-run with that field moved by ten percent while everything else stayed fixed: the calculated LDL goes across 86 mg/dL to 123 mg/dL, a swing of roughly 17.8 % around the 104 mg/dL baseline. That ratio is the practical definition of how much this input matters.
Is the LDL Friedewald result of 104 mg/dL good or bad?
Neither, on its own — the label “Friedewald LDL 104 mg/dL from 150 TG assumes VLDL = TG/5 — the estimate degrades as TG rise” is the band this figure falls in for the example inputs, and your own inputs will place you elsewhere on the same ladder. Judge the number against your history and your alternatives, and remember that a ten-percent error in Total cholesterol alone moves it by ≈17.8 %.
Can LDL Friedewald be negative or empty?
Yes, and that is informative rather than broken: a negative LDL Friedewald usually means the inputs encode an outflow or a shortfall, and the verdict band above labels exactly that situation instead of hiding it.
Is LDL Friedewald accurate?
The arithmetic is exact: LDL = TC − HDL − TG/5 (valid when TG <400) is evaluated with full floating-point precision and every substitution is printed in the worked example. What limits accuracy is input quality and the model’s assumptions, so treat the 104 mg/dL result as the correct answer to the question you typed — and check the assumptions section before acting on it.
Do I need to fast for Friedewald?
Fasting matters for TG accuracy; non-HDL and Martin-Hopkins tolerate nonfasting samples far better.
Why are labs moving to direct LDL?
Direct assays avoid the TG/5 assumption at high triglycerides and low LDL, though they carry their own calibration bias.
Is my data private on this page?
Yes — computation happens locally in your browser, with no account, no tracking of your inputs and nothing sent to a server. The printed formula is the whole story of what happens to your figures.
Glossary for LDL Friedewald
- Non-HDL cholesterol
- 134 mg/dL in the default LDL Friedewald calculation — one of the secondary figures an experienced reader checks before trusting the primary number.
- VLDL estimate
- 30 mg/dL in the default LDL Friedewald calculation — one of the secondary figures an experienced reader checks before trusting the primary number.
- Validity
- TG <400 — usable on the example inputs — a companion figure printed beside the headline of LDL Friedewald so that no result is read in isolation.
- Calculated LDL
- The primary output of this tool: 104 mg/dL for the default inputs, computed exactly from LDL = TC − HDL − TG/5 (valid when TG <400).
- Worked example
- The calculation written out in full so that nothing on this page has to be taken on trust.
- Verdict band
- The interpretation attached to a result (“Friedewald LDL 104 mg/dL from 150 TG assumes VLDL = TG/5 — the estimate degrades as TG rise” on these inputs), which turns a bare number into a position on a scale.
- Sensitivity (±10 %)
- How far the LDL Friedewald moves when a single input is nudged ten percent either way; the ranked list on this page is computed live from this engine.
Method, sources and what this tool cannot tell you
Everything above runs on one stated formula, applied without hidden coefficients: LDL = TC − HDL − TG/5 (valid when TG <400). Source of record: Friedewald Clin Chem 1972. Any other implementation of this model should return the same figure for the same inputs. If one does not, the difference is in its assumptions — which this page prints and that one probably does not.
Treat the output as a precise answer to the question you typed: exact arithmetic, transparent formula, published source, no hidden rounding. What that buys you is reproducibility — two people, two browsers, the same arithmetic, and a printed trail from inputs to result that either of them can audit.
Next steps after the calculation
Re-run the calculation with your own figures, stress the two most sensitive inputs by ±10 %, and only then act on the result.
This page was written for people who need one trustworthy number before their next decision, and the promise is that nothing above required trust. Bookmark the tool, re-run it whenever an input moves by more than a few percent, and keep the date with the number.