Build a TDEE and macro calculator for your coaching site

A TDEE calculator can give a prospective client a useful starting point before a coaching conversation. But a number without visible assumptions is easy to mistake for a prescription. Build the calculator around a method you can explain, show the assumptions beside the result, and treat the output as an estimate for discussion.

MyCalculators.app offers more than 200 ready-made calculators and lets users describe a custom calculator they need. Its homepage also says calculators can be shared by link or embedded on a site. Here is a practical way to specify a TDEE and macro tool without hiding the coaching decisions inside a black box.

1. Decide what the calculator should ask

Keep the first version focused. For a common adult estimate, inputs might include age, height, weight, and a selected activity level. If your method uses a sex-specific resting-energy equation, make that choice explicit and explain what a client should do if neither option fits. Do not imply the estimate is equally suitable for every person or circumstance.

Ask only for information needed by the calculation. Avoid collecting sensitive details just because a form can. If you plan to use the result in coaching, tell clients what the estimate means and how to follow up with you. Do not assume an embedded calculator stores or sends their answers; confirm your actual data handling separately.

2. Write down the formula before building

One widely used starting point is the Mifflin-St Jeor equation for resting energy expenditure. With weight in kilograms, height in centimeters, and age in years, its common forms are:

• Men: 10 × weight + 6.25 × height − 5 × age + 5.
• Women: 10 × weight + 6.25 × height − 5 × age − 161.

To estimate total daily energy expenditure, multiply that resting estimate by an activity factor. The factor is an approximation, not a measurement. Define what each activity choice means in your coaching practice; do not make clients guess whether a workout schedule or their whole-day movement should drive the selection.

Before writing a builder description, check that units are consistent and decide how the result will be rounded. A clear specification could say: “Build a TDEE estimate using weight in kilograms, height in centimeters, age in years, a selectable activity factor, and the Mifflin-St Jeor equation. Show the resting estimate, the activity factor, and the resulting daily estimate. Label the result as an estimate, not a medical recommendation.”

3. Add the macro calculation

Choose how the calculator will turn the calorie target into macros. A percentage split is straightforward to explain: assign a share of calories to protein, carbohydrate, and fat, then convert each share to grams. Protein and carbohydrate provide 4 calories per gram; fat provides 9.

For example, a 2,200-calorie target split 30% protein, 40% carbohydrate, and 30% fat produces 165 grams of protein, 220 grams of carbohydrate, and about 73 grams of fat. This is arithmetic, not a universal prescription. Replace the example split with the approach you use with clients, and make clear whether the client or coach sets it.

Include the formula in your description: “Calculate macro grams from the daily calorie target and the three percentage inputs. Check that the percentages total 100%, and show the gram conversion used.” If you prefer targets entered directly in grams, specify that instead. Avoid mixing both methods without explaining which one controls the result.

4. Describe the custom calculator

On MyCalculators.app, describe the calculator you need in plain language. State each input, its unit, the formula, the output labels, and any validation rules. Keep the first version small enough to test. If the builder offers a preview or generated result, inspect it rather than assuming your wording produced the intended model.

Math checks matter more than polished copy. Verify the resting-energy result against a hand calculation, then check that multiplying by the activity factor gives the displayed TDEE. Test the macro example above. Also try a missing input, an implausible value, and percentages that do not add to 100. Decide what the calculator should show in each case instead of letting a misleading result through.

For a closer look at why formula checks belong in the build process, see how deterministic math should be checked in customer-facing calculators.

5. Embed it with context

Once the calculation is right, use the calculator’s share or embed option to put it on your coaching site. Test the published version on a phone and desktop, and check that the input labels, units, and result remain readable. The ready-made calculators are described as mobile-friendly, but test your custom version in its actual placement rather than assuming every page layout behaves the same way.

Place a short note near the result: it is an estimate based on the inputs and selected assumptions, not an individualized health assessment. Give clients a clear next step, such as bringing the estimate to an intake conversation. That framing makes the calculator a useful start to coaching, not a substitute for it.