Perform fast calculations with our user-friendly online calculator! Conveniently crunch numbers and solve equations instantly. Ideal for quick math tasks, our tool simplifies your daily computations effortlessly. Try our intuitive calculator for accurate results on the go!
Use our Levothyroxine Dosage Calculator to estimate a daily dose from body weight. Learn the formula, steps, and example. Always follow your doctor's advice.
| Population | Typical Approach | Notes |
|---|---|---|
| Healthy, non-elderly adult, recent-onset hypothyroidism | ~1.6 mcg/kg/day full replacement, example 100-125 mcg/day for a 70 kg adult | The only population this weight-based estimate is labeled for |
| Older adults / cardiac disease | Fixed starting dose of 12.5-25 mcg/day (not weight-based) | Full-replacement dose may be <1 mcg/kg/day in elderly patients -- this calculator does not implement this separate rule |
| Titration (all populations) | Adjust by 12.5-25 mcg increments every 4-6 weeks | Until clinically euthyroid and serum TSH normalizes |
| Doses above 200 mcg/day | Described as seldom required | Flagged in this calculator's results as a review prompt, not an error |
A Levothyroxine Dosage Calculator helps you work out an estimated daily dose based on body weight and a dose factor. It can make the math quick and clear.
Levothyroxine is a drug that treats an underactive thyroid. It helps replace a hormone that your body lacks. Still, the right dose can vary from one person to the next.
Our free Levothyroxine Dosage Calculator shows the math in a few easy steps. It does not replace a doctor's advice or set your dose for you.
The core formula is simple:
Daily dose (mcg/day) = Weight (kg) × Dose factor (mcg/kg/day)
If your weight is in pounds (lb), first change it to kilograms (kg).
Weight (kg) = Weight (lb) ÷ 2.20462
Then use your weight in kg in the main formula.
For some healthy adults with an underactive thyroid, a full dose estimate may use 1.6 mcg per kg per day. This is not the right dose for everyone. Your age, heart health, test results, and other needs can change the dose your doctor picks.
Follow these five steps to work out an estimate.
Enter your weight. Type your body weight in the box.
Pick a unit. Choose kg or lb to match your weight.
Enter the dose factor. Use the factor set or advised by your health care team.
Run the calculation. Click the button to work out the daily dose estimate.
Read the result. Check the dose, units, and math shown on the screen.
The result can help you see how the math works. Do not use it to start, stop, or change your drug dose on your own.
Let’s look at a simple case.
An adult weighs 70 kg. For this example, the chosen factor is 1.6 mcg/kg/day.
Step 1: Write the formula.
Daily dose = Weight × Dose factor
Step 2: Add the values.
Daily dose = 70 × 1.6
Step 3: Work out the answer.
Daily dose = 112 mcg/day
The math gives an estimate of 112 mcg per day. It does not mean that this is the right dose for that person. A health care professional must decide the actual dose and tablet strength.
A Levothyroxine Dosage Calculator can make dose math easy to follow. It can convert weight from pounds to kg and show the steps used to find an estimate.
Think of it as a math aid, not a dose guide. Your doctor can use your thyroid blood tests, health needs, and response to care to set the right dose. Never change your dose based only on an online result.
It is an online tool that uses body weight and a dose factor to work out a daily dose estimate. It does not set a safe dose for each person.
Multiply weight in kg by the dose factor in mcg/kg/day. If your weight is in pounds, change it to kg first.
No. Weight is just one part of the picture. Age, heart health, thyroid tests, and other drugs can affect the dose you need.
It means micrograms per day. A microgram is a unit of mass. It is not the same as a milligram.
No. Talk to your prescriber before you change your dose. Too much or too little levothyroxine can harm your health.
Your health care team will set the right time for blood tests and dose checks. They may check your thyroid levels after a dose change.