Introduction
This LDL calculator finds your LDL cholesterol, often called the "bad" cholesterol, from a standard lipid panel. Just enter your total cholesterol, HDL cholesterol, and triglycerides. The tool does the math and shows your result in both mg/dL and mmol/L.
You can pick from three trusted formulas. The Friedewald formula is the classic one used by most labs. The Modified Friedewald formula works better when triglycerides are high. The Martin-Hopkins formula uses a table of 180 values to fine-tune the answer, so it is the most accurate choice and is set as the default.1
Along with your number, you get a risk rating from Very Low to Very High, a color scale, a step-by-step breakdown of the math, and charts that compare all three formulas. High LDL can build up in your arteries and raise your risk of heart attack and stroke, so knowing your level matters. To see how your numbers translate into long-term risk, pair this tool with our ASCVD Risk Calculator.
This tool is for learning only. Always talk to your doctor about your lab results and what they mean for you.
How to use our LDL Calculator
Enter three numbers from your lipid panel (total cholesterol, HDL, and triglycerides), and the calculator shows your estimated LDL cholesterol in mg/dL and mmol/L, your risk category, and the full math behind it.
Total Cholesterol (TC): Type the total cholesterol number from your blood test. A healthy level for adults aged 20 or older is less than 200 mg/dL.4
HDL Cholesterol (HDL): Type your HDL, the "good" cholesterol. It must be lower than your total cholesterol. An HDL under 40 mg/dL counts as low, and 60 mg/dL or above is best.4
Triglycerides (TG): Type your triglyceride level. For the best result, use a test taken after a 9 to 12 hour fast.4 A healthy level is less than 150 mg/dL.5 Triglycerides are also the key input for the VLDL Calculator.
Units (mg/dL or mmol/L): Pick the unit that matches your lab report. Tapping a unit button changes all three fields at once, so you never have to convert by hand.
Estimation Formula: Choose Martin-Hopkins (the default and most exact), Friedewald, or Modified Friedewald. If your triglycerides are above 400 mg/dL, the tool warns you and suggests a better formula.1
Calculate and Reset: Press Calculate to see your LDL result, gauge, charts, and step-by-step solution. Press Reset to clear every field and start over.
What Is LDL Cholesterol?
LDL stands for low-density lipoprotein. It is often called the "bad" cholesterol. LDL carries cholesterol through your blood. When there is too much of it, the extra cholesterol can stick to the walls of your arteries. Over time this build-up, called plaque, makes arteries narrow and stiff. That raises your risk of a heart attack or stroke. Keeping LDL low is one of the best ways to protect your heart.
How LDL Is Measured
A blood test called a lipid panel checks your fats. Most labs do not measure LDL directly. Instead, they measure three things and use math to estimate LDL:
- Total cholesterol (TC) – all the cholesterol in your blood.
- HDL cholesterol – the "good" cholesterol that clears fat out of your blood.
- Triglycerides (TG) – the main type of fat your body stores for energy.
Those three numbers are all you need to estimate LDL cholesterol.
The Three LDL Formulas
Different equations exist because triglycerides change how much cholesterol sits in VLDL particles. Each formula handles that differently.
- Friedewald Formula: LDL = TC − HDL − (TG ÷ 5).1 The oldest and most common method. It works well when triglycerides are normal, but it is not trusted above 400 mg/dL, and it can read too low when LDL is under 70 mg/dL.1
- Modified Friedewald: LDL = non-HDL × 90% − TG × 10%, a regression fit against directly measured LDL.2 A simple fix that works better when triglycerides are high.
- Martin-Hopkins: LDL = TC − HDL − (TG ÷ adjustable factor). Instead of always dividing by 5, it picks a number from a 180-cell table based on your triglycerides and non-HDL cholesterol. In the study introducing it, its risk classification matched direct measurement 91.7% of the time versus 85.4% for Friedewald, with the biggest gains at low LDL and high triglycerides, so it is the default here.1
LDL Cholesterol Ranges
| LDL (mg/dL) | LDL (mmol/L) | What It Means |
|---|---|---|
| Under 70 | Under 1.81 | Very low – a goal for people at high heart risk |
| 70–99 | 1.81–2.56 | Optimal |
| 100–129 | 2.59–3.34 | Near optimal |
| 130–159 | 3.36–4.11 | Borderline high |
| 160–189 | 4.14–4.89 | High |
| 190 and up | 4.91 and up | Very high |
Your own target may be lower if you have diabetes, past heart trouble, or family high cholesterol. Ask your doctor what number fits you.
Non-HDL Cholesterol
Non-HDL cholesterol is total cholesterol minus HDL. It counts every "bad" particle, not just LDL. Many doctors watch it closely, especially when triglycerides are high. For men aged 20 or older, MedlinePlus puts the healthy non-HDL level at less than 130 mg/dL against an LDL under 100.4 That is where the rule of thumb comes from: a non-HDL goal about 30 mg/dL above the LDL goal.
Fasting Matters
Triglycerides jump after you eat. For the most accurate estimate, blood should be drawn after a 9 to 12 hour fast.4 A non-fasting test can still be useful, but a high triglyceride reading can throw off the Friedewald result.
Ways to Lower LDL
- Eat less saturated fat from fatty meat, butter, and full-fat dairy. Cut out trans fats.
- Eat more fiber: oats, beans, fruit, and vegetables.
- Move your body about 30 minutes most days.
- Reach and keep a healthy weight. Check where you stand with the BMI Calculator.
- Stop smoking.
- Take statins or other medicine if your doctor prescribes them.
Unit Conversion
The United States reports cholesterol in mg/dL. Most other countries use mmol/L. To switch, divide cholesterol values by 38.67 and triglycerides by 88.57.
This tool gives an estimate for learning only. It does not replace a blood test or advice from your doctor.