LDL Calculator

How to use this LDL cholesterol calculator

What this calculator does

This calculator estimates low-density lipoprotein cholesterol (LDL-C) from three values found on a lipid panel: Total cholesterol, High-density lipoproteins (HDL), and Triglycerides (TG). It uses the Friedewald relationship, which treats total cholesterol as the sum of HDL cholesterol, LDL cholesterol, and an estimated very-low-density lipoprotein component. The result is a mathematical estimate, not a diagnosis, cardiovascular-risk score, treatment target, or substitute for a directly measured LDL result. The CDC's NHANES laboratory documentation describes the Friedewald calculation and its triglyceride limitation in detail in its triglyceride and LDL laboratory methods.

When to use it

Use the calculator to check an LDL value when a lipid report provides total cholesterol, HDL, and triglycerides but not a calculated LDL; to reproduce a Friedewald estimate for a teaching example; to compare how a corrected lipid-panel entry changes the estimate; or to convert one calculation between mg/dL and mmol/L before discussing the report with a health professional. It is not designed to decide whether medication is needed or to replace individualized clinical assessment.

How to calculate

1. The calculator opens with a complete demonstration set – 230 mg/dL total cholesterol, 47 mg/dL HDL, and 123 mg/dL triglycerides – so the first result and the Excel export are immediately usable.
2. Replace each demonstration value with the corresponding result from the same lipid panel. The calculation updates as you type. Enter a period as the decimal separator; standard comma thousands grouping is accepted, but scientific notation and ambiguous decimal-comma input are rejected.
3. Use Units to switch between mg/dL and mmol/L. The current values are converted rather than merely relabeled, including the different conversion used for triglycerides.
4. Read Estimated LDL cholesterol first, then review Non-HDL cholesterol, the Estimated VLDL component, and the composition table/chart to understand the arithmetic behind the estimate.
5. Select Download Excel to export the current validated inputs, results, component breakdown, and method notes as an .xlsx workbook. Reset clears the demonstration and all calculated content. After Reset, Excel download stays unavailable until a complete valid set of inputs has been entered again.

Input guide

Total cholesterol is required. Enter a nonnegative laboratory concentration greater than zero, in the unit currently selected. A realistic example is 230 mg/dL. Higher total cholesterol raises the calculated LDL when HDL and triglycerides stay unchanged. A common mistake is mixing a total-cholesterol result from one date with HDL or triglycerides from another panel.

High-density lipoproteins (HDL) is required and uses the same cholesterol unit as total cholesterol. The demonstration value is 47 mg/dL. Increasing HDL lowers the calculated LDL because HDL is subtracted from total cholesterol. HDL cannot exceed total cholesterol in a coherent Friedewald calculation; if it does, the calculator asks you to review the entries.

Triglycerides (TG) is required. The demonstration value is 123 mg/dL. In the mg/dL form of the Friedewald relationship, TG is divided by five to estimate the VLDL-cholesterol component, so higher TG lowers the calculated LDL when total cholesterol and HDL stay fixed. This implementation accepts TG from 0 through 400 mg/dL-equivalent and blocks higher values because the conventional Friedewald method is not considered reliable beyond that range. Do not paste a unit symbol into the field; use the separate unit selector.

Units is a required two-choice control. Choose mg/dL for the conventional U.S. laboratory format or mmol/L for SI reporting. When you switch units, the calculator converts the values already entered. Cholesterol concentrations use a different molecular conversion factor from triglycerides, so manual relabeling without conversion would be incorrect.

Output guide

Estimated LDL cholesterol is the primary result. It is an estimated concentration driven by all three inputs. Non-HDL cholesterol equals total cholesterol minus HDL and is shown as a supporting arithmetic value. Estimated VLDL component is the TG-derived amount subtracted by the Friedewald model; it is an estimate, not a measured VLDL test. In the Cholesterol composition table, Component names the LDL, HDL, or estimated VLDL portion; Estimated value gives the concentration in the selected unit; and Share of total shows each positive component as a percentage of total cholesterol. The donut chart uses those same three keyed values, so a larger arc means a larger arithmetic share of the current total – not a recommended target or risk score.

Worked example

With the startup values, the estimated VLDL component is 123 ÷ 5 = 24.6 mg/dL. The Friedewald calculation is therefore 230 – 47 – 24.6 = 158.4 mg/dL estimated LDL cholesterol. Non-HDL cholesterol is 230 – 47 = 183.0 mg/dL. The three composition values – 158.4 LDL, 47.0 HDL, and 24.6 estimated VLDL – sum back to the 230.0 mg/dL total, which is also the invariant used to build the table and chart.

Learn more

For background on what LDL, HDL, and triglycerides represent, see the CDC's overview of LDL, HDL, and triglycerides. For general adult laboratory reference levels and why targets can differ by age and health history, MedlinePlus provides a practical guide to understanding cholesterol levels.