If you're keeping an eye on your cholesterol levels, you know how important it is to track your LDL or "bad" cholesterol. Thankfully, there's a simple online tool that can help - the LDL calculator.
LDL stands for low-density lipoprotein, which is one of the key cholesterol markers that healthcare providers use to assess cardiovascular risk. While our bodies need some LDL to function properly, having too much can lead to artery-clogging plaque buildup over time. That's why guidelines recommend keeping your LDL level below 100 mg/dL if you're at low risk for heart disease, or even lower if you have other risk factors.
An LDL calculator is an online tool that calculates your level of low-density lipoprotein (LDL) cholesterol based on the results from a standard cholesterol blood test.
To use an LDL calculator, you typically input three values from your cholesterol test results:
- Total cholesterol
- HDL (high-density lipoprotein) cholesterol - the "good" cholesterol
- Triglycerides
The calculator then uses a formula to estimate your LDL cholesterol level from those three numbers.
Knowing your LDL level is important because LDL is often referred to as the "bad" cholesterol. High levels of LDL can build up on the walls of your arteries, increasing your risk of heart disease and stroke.
Most guidelines recommend keeping your LDL cholesterol below 100 mg/dL if you have a high risk of heart disease, or below 130 mg/dL if you are at lower risk.
The Friedewald equation
The Friedewald equation is the formula typically used by LDL cholesterol calculators to estimate LDL-C levels from basic cholesterol test results.
The full Friedewald equation is:
LDL = Total Cholesterol - HDL - (Triglycerides/5)
Where:
- LDL = Low-density lipoprotein cholesterol (mg/dL)
- Total Cholesterol = Total cholesterol level (mg/dL)
- HDL = High-density lipoprotein cholesterol (mg/dL)
- Triglycerides = Triglyceride level (mg/dL)
This equation, developed by Dr. William P. Friedewald in 1972, provides an estimate of LDL without having to do more complex testing.
It makes some key assumptions, including:
- Triglyceride levels are under 400 mg/dL
- Cholesterol measurements are taken after a 12-hour fast
While not as accurate as direct LDL measurement, the Friedewald calculation is convenient and correlates reasonably well with actual LDL-C levels for most people.
The Triglycerides/5 component accounts for the cholesterol content of very low-density lipoproteins (VLDL).
Most online LDL calculators and apps utilize this Friedewald formula behind the scenes to estimate LDL from the more basic cholesterol numbers.
What do my cholesterol numbers mean?
Here are healthy cholesterol levels based on your age and gender:
Anyone 19 years of age or younger:
| Type of Cholesterol | Healthy Level |
|---|---|
| Total Cholesterol | Less than 170mg/dL |
| Non-HDL | Less than 120mg/dL |
| LDL | Less than 100mg/dL |
| HDL | More than 45mg/dL |
Men 20 years and older:
| Type of Cholesterol | Healthy Level |
|---|---|
| Total Cholesterol | 125 to 200mg/dL |
| Non-HDL | Less than 130mg/dL |
| LDL | Less than 100mg/dL |
| HDL | 40mg/dL or higher |
Women 20 years and older:
| Type of Cholesterol | Healthy Level |
|---|---|
| Total Cholesterol | 125 to 200mg/dL |
| Non-HDL | Less than 130mg/dL |
| LDL | Less than 100mg/dL |
| HDL | 50mg/dL or higher |