How to Use the Total T4 Unit Conversion Calculator
Choose the conversion direction, enter the Total T4 value from your lab report, and read the result instantly. The calculator supports both µg/dL to nmol/L and nmol/L to µg/dL.
This page is focused on Total T4, also called total thyroxine. It is not the same as Free T4, which measures only the unbound fraction of thyroxine. If your lab report lists Free T4, use the Free T4 Unit Conversion Calculator instead.
Total T4 Conversion Formula
Total T4 is commonly reported in µg/dL in conventional lab reports and nmol/L in many SI-style or international reports. The conversion uses the molecular weight of thyroxine, about 776.87 g/mol.
Total T4 nmol/L = Total T4 µg/dL x 12.87 Total T4 µg/dL = Total T4 nmol/L ÷ 12.87 The same relationship can also be derived from nmol/L = µg/dL x 10,000 ÷ 776.87.
Example Total T4 Conversion
If your Total T4 result is 8.0 µg/dL, multiply by 12.87:
8.0 x 12.87 = 102.98 nmol/L For the reverse direction, divide by 12.87. A Total T4 value of 100 nmol/L is about 7.77 µg/dL.
Total T4 µg/dL to nmol/L Chart
Use this chart to compare common Total T4 values between µg/dL and nmol/L. Reference ranges vary by lab, assay method, age, pregnancy status, and binding protein levels.
| Total T4 µg/dL | Total T4 nmol/L | Note |
|---|---|---|
| 3 µg/dL | 38.6 nmol/L | Often below many adult reference ranges |
| 4 µg/dL | 51.5 nmol/L | Lower area in many adult reports |
| 5 µg/dL | 64.4 nmol/L | Common low-normal comparison value |
| 6 µg/dL | 77.2 nmol/L | Common normal-area value |
| 8 µg/dL | 103.0 nmol/L | Common normal-area value |
| 10 µg/dL | 128.7 nmol/L | Common normal-area value |
| 12 µg/dL | 154.5 nmol/L | Upper area in many adult reports |
| 15 µg/dL | 193.1 nmol/L | Elevated in many clinical contexts |
| 20 µg/dL | 257.4 nmol/L | Markedly elevated in many reports |
nmol/L to µg/dL Reverse Chart
If your thyroid report uses nmol/L and you want the conventional µg/dL value, use this reverse chart.
| Total T4 nmol/L | Total T4 µg/dL |
|---|---|
| 50 nmol/L | 3.9 µg/dL |
| 75 nmol/L | 5.8 µg/dL |
| 100 nmol/L | 7.8 µg/dL |
| 125 nmol/L | 9.7 µg/dL |
| 150 nmol/L | 11.7 µg/dL |
| 175 nmol/L | 13.6 µg/dL |
| 200 nmol/L | 15.5 µg/dL |
| 250 nmol/L | 19.4 µg/dL |
| 300 nmol/L | 23.3 µg/dL |
Total T4 vs Free T4
Total T4 measures both protein-bound and unbound thyroxine in the blood. Free T4 measures only the unbound fraction. These tests use different units, different reference ranges, and can behave differently when thyroid-binding proteins change.
For Free T4 unit conversion, use the dedicated Free T4 Unit Conversion Calculator. Do not compare a Total T4 result directly with a Free T4 reference range.
Total T4 in a Thyroid Panel
Total T4 is usually interpreted with TSH and other thyroid tests such as Free T4, Total T3, or Free T3. The TSH Unit Conversion Calculator, Total T3 Unit Conversion Calculator, and Free T3 Unit Conversion Calculator are useful companion pages when you are comparing a full thyroid panel. Total T4 may be reviewed when thyroid disease, medication effects, pregnancy, estrogen therapy, or binding protein changes are part of the clinical question.
Unit conversion helps compare reports, but it does not decide whether a thyroid result is normal or abnormal. Always compare your result with the reference range printed on the same lab report.
Common Mistakes to Avoid
Do not use the Free T4 pmol/L conversion factor for Total T4 µg/dL. Free T4 and Total T4 are related tests, but they are reported in different unit systems and reference ranges.
Do not mix Total T4 and Total T3 conversions. T4 and T3 have different molecular weights, so their conversion factors are different. For triiodothyronine results, use the Total T3 Unit Conversion Calculator.
Frequently Asked Questions
How do you convert Total T4 µg/dL to nmol/L?
Multiply the Total T4 value in µg/dL by 12.87. For example, 8 µg/dL is about 102.98 nmol/L.
How do you convert Total T4 nmol/L to µg/dL?
Divide the nmol/L value by 12.87. For example, 100 nmol/L is about 7.77 µg/dL.
What is 10 µg/dL Total T4 in nmol/L?
10 µg/dL Total T4 equals approximately 128.7 nmol/L.
Is Total T4 the same as Free T4?
No. Total T4 includes bound and unbound thyroxine, while Free T4 measures only the unbound fraction. They require different reference ranges and usually different unit conversions.
Can this calculator diagnose thyroid disease?
No. This tool only converts units. Thyroid interpretation requires clinical context and usually includes TSH, Free T4, symptoms, medication history, pregnancy status, and other clinical details.
Conclusion
This Total T4 unit conversion calculator helps you compare thyroid lab results across µg/dL and nmol/L reporting systems. Use it for accurate unit conversion, then compare the converted value with the reference range from your own report.
For clinical interpretation, Total T4 should be reviewed with TSH, Free T4, Total T3, symptoms, medications, and guidance from a qualified healthcare professional.