Friedewald LDL Cholesterol Calculator
Enter total cholesterol (TC), HDL and triglycerides (TG) from your lipid panel; the tool applies the 1972 Friedewald equation (LDL = TC − HDL − TG / 5 in mg/dL or / 2.2 in mmol/L) to estimate the low-density lipoprotein cholesterol ("bad" LDL-C) and grades it using the five NCEP ATP III bands — optimal, near-optimal, borderline high, high and very high. The output also surfaces the implied VLDL and non-HDL values so you can cross-check the rest of the report.
Check inputs: total cholesterol, HDL and triglycerides must all be > 0, and HDL must be less than total cholesterol.
Estimated LDL-C
120
mg/dL
Near optimal
Estimated VLDL (TG ÷ 5 or 2.2) 30
Non-HDL (TC − HDL) 150
NCEP ATP III risk band (mg/dL)
<100 Near optimal
100–129 Borderline high
130–159 High
160–189 Very high
≥190
Formula: Friedewald 1972 (Clin Chem 18:499). Bands: NCEP ATP III (JAMA 2001). Educational use only — not a substitute for clinical judgement.
Formula
mg/dL: LDL-C = TC − HDL − TG / 5 mmol/L: LDL-C = TC − HDL − TG / 2.2 VLDL-C ≈ TG / 5 (mg/dL) or TG / 2.2 (mmol/L) Non-HDL-C = TC − HDL
- · The equation assumes triglycerides come entirely from VLDL with a VLDL-C : VLDL-TG ratio of about 1 : 5 (mg/dL). It breaks down when TG > 400 mg/dL (> 4.52 mmol/L) — the calculator surfaces a warning in that range.
- · Unit conversion: mg/dL × 0.02586 = mmol/L (TC / HDL / LDL); mg/dL × 0.01129 = mmol/L (TG). UK, EU and most HK public-hospital reports use mmol/L; US and most HK private labs use mg/dL.
- · NCEP ATP III bands are a coarse risk screen. Adults with established cardiovascular disease, diabetes or chronic kidney disease are usually advised to aim for LDL-C < 70 mg/dL (< 1.8 mmol/L) — below the "optimal" band.
- · Non-fasting samples can inflate TG and therefore under-estimate LDL. Most lipid panels are taken after a 9–12 h fast (water-only) for comparable results.
- · The 2013 Martin / Hopkins equation replaces the fixed TG/5 with a 180-cell adjustable lookup, and is materially more accurate at low LDL and high TG. The 2022 US NLA Scientific Statement now prefers Martin/Hopkins over Friedewald where the tools are available.
- · References: Friedewald WT, Levy RI, Fredrickson DS. Clin Chem 1972;18:499–502; NCEP ATP III, JAMA 2001;285:2486; Martin SS et al. JAMA 2013;310:2061; NLA Scientific Statement 2022.
Frequently asked
My lab report already lists an LDL number — is the Friedewald calculation still useful?
Most labs report "LDL-C" as a derived number from Friedewald (or the newer Martin/Hopkins refinement), not as a direct measurement. Running this calculator should give a value within a few units of the printed LDL — a meaningful difference (e.g. > 10 mg/dL) usually means the lab used Martin/Hopkins or NIH Equation 2 instead of classic Friedewald. A truly direct measurement requires β-quantification ultracentrifugation or a direct LDL assay, which is more expensive and reserved for cases of very high TG or known Friedewald unreliability. The calculator is also useful for "what-if" scenarios: see how an increase in HDL or drop in TG would shift LDL.
Why does the formula break down above TG 400 mg/dL?
Friedewald assumes a VLDL-C : VLDL-TG ratio of about 1 : 5 (mg/dL). In the normal range almost all TG is carried by VLDL and the ratio is stable. Above TG 400 mg/dL, a growing share of TG sits in chylomicrons or VLDL remnants, which have a very different cholesterol : TG composition; the fixed TG/5 then overshoots the true VLDL-C and under-estimates LDL. For TG 400–800 mg/dL the Martin/Hopkins 180-cell lookup is still usable; above 800 mg/dL ultracentrifugation is usually needed, and type III or type V hyperlipoproteinaemia should be excluded.
Why do some clinicians focus on non-HDL rather than LDL?
Non-HDL (TC − HDL) sums all atherogenic cholesterol — LDL, VLDL, IDL, Lp(a). It has three advantages: (1) no fast required; (2) it stays accurate when triglycerides are elevated (Friedewald drifts once TG > 200 mg/dL); (3) it captures the higher residual risk in people with diabetes or metabolic syndrome, who often have a "normal" LDL but elevated VLDL. NCEP ATP III, ESC 2019 and AHA/ACC 2018 all list non-HDL as a secondary treatment goal — typically the LDL target + 30 mg/dL (or + 0.8 mmol/L). The calculator surfaces both LDL and non-HDL so you can cross-check.
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