LDL Calculator
Free Ldlcalculator Calculator with medically-sourced formulas. Enter your measurements for personalized, accurate health insights.
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The Friedewald equation estimates LDL cholesterol by subtracting HDL and estimated VLDL (triglycerides divided by 5) from total cholesterol. All values are in mg/dL. This formula is valid when triglycerides are below 400 mg/dL.
Last reviewed: January 2026
Worked Examples
Example 1: Standard Lipid Panel LDL Calculation
Example 2: High Risk Patient LDL Assessment
Background & Theory
The LDL Calculator applies the following established principles and formulas. Health and medicine calculators are grounded in validated physiological measurement methods established through decades of clinical research. Body Mass Index, or BMI, is calculated by dividing weight in kilograms by height in meters squared (kg/m²), a formula originating from Adolphe Quetelet's 19th-century statistical work and later codified by the WHO into standard classifications: underweight below 18.5, normal weight 18.5 to 24.9, overweight 25 to 29.9, and obese at 30 and above. Basal Metabolic Rate quantifies the minimum energy required to sustain life at rest. The Mifflin-St Jeor equation, published in 1990 and widely regarded as the most accurate for most adults, calculates BMR as (10 × weight in kg) + (6.25 × height in cm) − (5 × age) ± sex adjustment. The older Harris-Benedict equations, revised in 1984 by Roza and Shizgal, remain in common use. Total Daily Energy Expenditure is derived by multiplying BMR by a physical activity factor ranging from 1.2 for sedentary individuals to 1.9 for extremely active ones, following the methodology validated by doubly labeled water studies. Body fat percentage can be estimated without laboratory equipment using the U.S. Navy circumference method, which uses neck, waist, and hip measurements, or via BMI-derived equations adjusted for age and sex. The Jackson-Pollock skinfold method offers higher precision with calipers. Blood pressure classification, according to the American College of Cardiology and the 2017 ACC/AHA guidelines, defines normal as below 120/80 mmHg, elevated as 120 to 129 systolic, and hypertension stage 1 as 130 to 139 systolic or 80 to 89 diastolic. Target heart rate zones for aerobic exercise are derived from maximum heart rate estimates, most commonly using the formula 220 minus age in years, with moderate-intensity training typically defined as 50 to 70 percent of maximum heart rate and vigorous intensity at 70 to 85 percent, consistent with CDC and American Heart Association guidelines. These thresholds guide safe and effective cardiovascular conditioning.
History
The history behind the LDL Calculator traces back through the following developments. The history of health measurement stretches back to ancient Greece, where Hippocrates around 400 BCE laid the foundation for observational medicine by systematically recording patient symptoms, diet, and environment. His humoral theory, though scientifically superseded, established the principle that the body operates as an interconnected system subject to measurable imbalance. The transformation toward modern medicine accelerated in the 19th century. Louis Pasteur and Robert Koch developed germ theory in the 1860s and 1870s, identifying microorganisms as disease agents and enabling targeted interventions. Florence Nightingale, working during the Crimean War in the 1850s, introduced statistical analysis to nursing practice, demonstrating through data visualization that sanitation reduced mortality. Her work is foundational to evidence-based health measurement. The discovery of vitamins in the early 20th century, beginning with Casimir Funk's coinage of the term in 1912 and culminating in the isolation of vitamins A through K, created the field of nutritional science and gave rise to dietary reference intake frameworks. The World Health Organization, founded in 1948, subsequently established global standards for health metrics, disease classification through the International Classification of Diseases, and recommended daily allowances. The BMI as a clinical screening tool gained traction in the 1970s through Ancel Keys' large-scale epidemiological work, which validated Quetelet's index as a population-level obesity indicator. Through the 1980s and 1990s, the Framingham Heart Study produced landmark data linking cholesterol, blood pressure, and lifestyle factors to cardiovascular disease risk, directly shaping the numeric thresholds still used in health calculators. The evidence-based medicine movement, formalized by Gordon Guyatt and colleagues at McMaster University in the early 1990s, demanded that all health recommendations derive from systematically graded clinical evidence. The digital health era beginning in the 2000s brought these formulas to consumer devices, wearable sensors, and smartphone applications, expanding access to health self-monitoring on a global scale and enabling population-level data collection that continues to refine clinical reference ranges.
Frequently Asked Questions
Formula
LDL = Total Cholesterol - HDL - (Triglycerides / 5)
The Friedewald equation estimates LDL cholesterol by subtracting HDL and estimated VLDL (triglycerides divided by 5) from total cholesterol. All values are in mg/dL. This formula is valid when triglycerides are below 400 mg/dL.
Worked Examples
Example 1: Standard Lipid Panel LDL Calculation
Problem: A patient has Total Cholesterol of 220 mg/dL, HDL of 55 mg/dL, and Triglycerides of 150 mg/dL. Calculate the estimated LDL cholesterol.
Solution: Using Friedewald equation: LDL = TC - HDL - (TG / 5)\nLDL = 220 - 55 - (150 / 5)\nLDL = 220 - 55 - 30\nLDL = 135 mg/dL\nVLDL = 150 / 5 = 30 mg/dL\nNon-HDL = 220 - 55 = 165 mg/dL\nTC/HDL Ratio = 220 / 55 = 4.0
Result: LDL = 135 mg/dL (Borderline High) | Non-HDL = 165 mg/dL | TC/HDL Ratio = 4.0 (Average Risk)
Example 2: High Risk Patient LDL Assessment
Problem: A diabetic patient has Total Cholesterol of 250 mg/dL, HDL of 38 mg/dL, and Triglycerides of 300 mg/dL. Calculate LDL and assess risk.
Solution: Using Friedewald equation: LDL = TC - HDL - (TG / 5)\nLDL = 250 - 38 - (300 / 5)\nLDL = 250 - 38 - 60\nLDL = 152 mg/dL\nUsing Iranian formula: LDL = 250/1.19 + 300/1.9 - 38/1.1 - 38\nLDL = 210.1 + 157.9 - 34.5 - 38 = 295.5 (Note: discrepancy suggests direct LDL testing needed)\nTC/HDL Ratio = 250 / 38 = 6.58 (High Risk)
Result: LDL = 152 mg/dL (Borderline High) | TC/HDL Ratio = 6.58 (High Risk) | Target for diabetics: < 70 mg/dL
Frequently Asked Questions
What is LDL cholesterol and why is it important?
LDL (Low-Density Lipoprotein) cholesterol is often called bad cholesterol because it carries cholesterol particles throughout your body and can build up in the walls of your arteries. This buildup, known as atherosclerosis, narrows the arteries and increases the risk of heart attack and stroke. High LDL levels are one of the most significant modifiable risk factors for cardiovascular disease. The American Heart Association recommends keeping LDL below 100 mg/dL for most adults, and below 70 mg/dL for those at very high cardiovascular risk. Regular monitoring through blood tests helps track your levels over time.
How does the Friedewald equation calculate LDL cholesterol?
The Friedewald equation is the most widely used method to estimate LDL cholesterol from a standard lipid panel. The formula is LDL = Total Cholesterol minus HDL minus (Triglycerides divided by 5), where all values are in mg/dL. This equation works by subtracting the known cholesterol fractions (HDL and VLDL) from total cholesterol, with VLDL estimated as one-fifth of triglycerides. The formula is accurate when triglycerides are below 400 mg/dL, but becomes unreliable at higher triglyceride levels. In those cases, a direct LDL measurement through laboratory testing is recommended instead.
What is the difference between Friedewald and Iranian formula for LDL?
The Iranian formula (also known as the Anandaraja equation) was developed as an alternative to the Friedewald equation and uses a different mathematical approach: LDL = TC/1.19 + TG/1.9 - HDL/1.1 - 38. Some studies suggest the Iranian formula may be more accurate when triglyceride levels are between 200 and 400 mg/dL, where the Friedewald equation can underestimate LDL. However, the Friedewald equation remains the clinical standard worldwide. Comparing results from both formulas can give you a range of your estimated LDL, which is especially useful when triglycerides are moderately elevated.
What are optimal LDL cholesterol levels for heart health?
According to the American Heart Association and National Lipid Association guidelines, LDL cholesterol levels are classified as follows: below 100 mg/dL is optimal, 100 to 129 mg/dL is near optimal, 130 to 159 mg/dL is borderline high, 160 to 189 mg/dL is high, and 190 mg/dL or above is very high. For individuals who have already had a cardiovascular event or have diabetes, the target LDL is typically below 70 mg/dL. Lifestyle changes including diet, exercise, and weight management can lower LDL by 10 to 20 percent, while statin medications can reduce LDL by 30 to 50 percent or more.
Why are triglycerides important in LDL calculation?
Triglycerides play a crucial role in LDL estimation because the Friedewald equation uses triglyceride levels to estimate VLDL cholesterol, which is then subtracted from total cholesterol. The assumption is that VLDL equals triglycerides divided by 5, which holds true for most people with normal to moderately elevated triglycerides. When triglycerides exceed 400 mg/dL, this ratio breaks down and the calculated LDL becomes inaccurate. High triglycerides independently increase cardiovascular risk and are often associated with metabolic syndrome, obesity, and insulin resistance. Fasting for 9 to 12 hours before testing ensures the most accurate triglyceride measurement.
How can I lower my LDL cholesterol naturally?
Several evidence-based strategies can lower LDL cholesterol without medication. A heart-healthy diet rich in soluble fiber from oats, beans, and fruits can reduce LDL by 5 to 10 percent. Replacing saturated fats with unsaturated fats from olive oil, nuts, and avocados further reduces LDL. Regular aerobic exercise of 150 minutes per week can lower LDL by 5 to 10 percent and raise protective HDL. Losing 5 to 10 percent of body weight if overweight has significant benefits for all lipid levels. Plant sterols and stanols found in fortified foods can reduce LDL by an additional 6 to 15 percent when consumed at 2 grams daily.
References
Reviewed by Rahul Singh, Health & Wellness Specialist · Editorial policy