Friedewald (1972) Formula: LDL = TC - HDL - TG/5.0 (mg/dL) Reference.

"Iranian" (2008) Formula:    LDL = TC/1.19 + TG/1.9 – HDL/1.1 – 38 (mg/dL) Reference.

Comment:
For those of us on a low carbohydrate lifestyle - the "Iranian" formula used above can perhaps give a better "estimation" of LDL when our Triglycerides are nice and low. However the Iranian study was made with people with elevated cholesterol. Hopefully one day, a study may be done with "healthy" people (and thus develop a more accurate formula)!

TEST CASE: (to ensure calculator is working correctly on your computer).
Total Cholesterol = 201 (mg/dL)
HDL Cholesterol = 74 (mg/dL)
       Triglycerides = 44 (mg/dL)
LDL (estimated) = 118.2 (mg/dL) as per Friedewald formula
LDL (estimated) = 86.79273048932494 (mg/dL) as per "Iranian" formula
Full accuracy is shown, normally we would round-off to 1 (mg/dL)