Add Free Calculators to Your Website
Copy one line of code. Get a fully-functional health calculator on your site instantly — free forever, no API key, no sign-up.
How to embed a calculator
Choose a calculator
Pick any calculator below that fits your content.
Copy the embed code
Click 'Copy Code' — one <iframe> tag is all you need.
Paste into your site
Works on WordPress, Webflow, Squarespace, HTML — anywhere that allows iframes.
Available calculators
BMI Calculator
Calculate your Body Mass Index using the WHO standard formula. Get your weight category and healthy weight range instantly.
<iframe src="https://fitfueltools.com/embed/bmi-calculator" width="100%" height="600" frameborder="0" style="border-radius:12px;border:1px solid #e5e7eb;" title="BMI Calculator — FitFuel Tools" loading="lazy"></iframe>
Calorie Calculator
Calculate your BMR and TDEE using the Mifflin-St Jeor equation. Get personalized daily calorie targets for any goal.
<iframe src="https://fitfueltools.com/embed/calorie-calculator" width="100%" height="600" frameborder="0" style="border-radius:12px;border:1px solid #e5e7eb;" title="Calorie Calculator — FitFuel Tools" loading="lazy"></iframe>
TDEE Calculator
Calculate your Total Daily Energy Expenditure. The most important number for setting any nutrition goal.
<iframe src="https://fitfueltools.com/embed/tdee-calculator" width="100%" height="600" frameborder="0" style="border-radius:12px;border:1px solid #e5e7eb;" title="TDEE Calculator — FitFuel Tools" loading="lazy"></iframe>
Macro Calculator
Calculate your optimal protein, carbohydrate, and fat targets based on your calorie goal and fitness objective.
<iframe src="https://fitfueltools.com/embed/macro-calculator" width="100%" height="600" frameborder="0" style="border-radius:12px;border:1px solid #e5e7eb;" title="Macro Calculator — FitFuel Tools" loading="lazy"></iframe>
Calorie Deficit Calculator
Calculate your daily calorie deficit to lose weight at a safe, sustainable rate without sacrificing muscle.
<iframe src="https://fitfueltools.com/embed/calorie-deficit-calculator" width="100%" height="600" frameborder="0" style="border-radius:12px;border:1px solid #e5e7eb;" title="Calorie Deficit Calculator — FitFuel Tools" loading="lazy"></iframe>
Weight Loss Calculator
Calculate how long it will take to reach your goal weight, your required daily calorie deficit, and your projected weekly fat loss rate.
<iframe src="https://fitfueltools.com/embed/weight-loss-calculator" width="100%" height="600" frameborder="0" style="border-radius:12px;border:1px solid #e5e7eb;" title="Weight Loss Calculator — FitFuel Tools" loading="lazy"></iframe>
Muscle Gain Calculator
Calculate your optimal calorie surplus for lean muscle gain, your natural muscle-building potential, and required protein intake.
<iframe src="https://fitfueltools.com/embed/muscle-gain-calculator" width="100%" height="600" frameborder="0" style="border-radius:12px;border:1px solid #e5e7eb;" title="Muscle Gain Calculator — FitFuel Tools" loading="lazy"></iframe>
Daily Calorie Calculator
Find out exactly how many calories you need per day to lose weight, maintain, or build muscle — personalised to your stats and activity level.
<iframe src="https://fitfueltools.com/embed/daily-calorie-calculator" width="100%" height="600" frameborder="0" style="border-radius:12px;border:1px solid #e5e7eb;" title="Daily Calorie Calculator — FitFuel Tools" loading="lazy"></iframe>
Healthy Weight Calculator
Find your healthy weight range using 5 validated methods — BMI range, Hamwi, Devine, Robinson, and Miller formulas — with frame size adjustments.
<iframe src="https://fitfueltools.com/embed/healthy-weight-calculator" width="100%" height="600" frameborder="0" style="border-radius:12px;border:1px solid #e5e7eb;" title="Healthy Weight Calculator — FitFuel Tools" loading="lazy"></iframe>
Sleep Calculator
Calculate the best times to fall asleep or wake up based on 90-minute sleep cycles. Wake at the right point to feel dramatically more refreshed.
<iframe src="https://fitfueltools.com/embed/sleep-calculator" width="100%" height="600" frameborder="0" style="border-radius:12px;border:1px solid #e5e7eb;" title="Sleep Calculator — FitFuel Tools" loading="lazy"></iframe>
Macro Ratio Calculator
Find the optimal macronutrient ratios for your goal — fat loss, muscle gain, keto, endurance, or maintenance — with daily gram targets.
<iframe src="https://fitfueltools.com/embed/macro-ratio-calculator" width="100%" height="600" frameborder="0" style="border-radius:12px;border:1px solid #e5e7eb;" title="Macro Ratio Calculator — FitFuel Tools" loading="lazy"></iframe>
TDEE Calculator for Women
Calculate your Total Daily Energy Expenditure as a woman — with female-specific metabolic differences, activity levels, and goal-based calorie targets.
<iframe src="https://fitfueltools.com/embed/tdee-calculator-women" width="100%" height="600" frameborder="0" style="border-radius:12px;border:1px solid #e5e7eb;" title="TDEE Calculator for Women — FitFuel Tools" loading="lazy"></iframe>
Protein Calculator
Calculate your optimal daily protein intake in grams based on body weight, goal, and activity — with per-meal targets and food source examples.
<iframe src="https://fitfueltools.com/embed/protein-calculator" width="100%" height="600" frameborder="0" style="border-radius:12px;border:1px solid #e5e7eb;" title="Protein Calculator — FitFuel Tools" loading="lazy"></iframe>
Calories Burned Exercise Calculator
Calculate calories burned during 40+ exercises including running, cycling, swimming, HIIT, strength training, yoga, and walking — personalised by weight.
<iframe src="https://fitfueltools.com/embed/calorie-burn-calculator" width="100%" height="600" frameborder="0" style="border-radius:12px;border:1px solid #e5e7eb;" title="Calories Burned Exercise Calculator — FitFuel Tools" loading="lazy"></iframe>
Biological Age Calculator
Find out how old your body really is. Estimate your biological age from 12 lifestyle factors including exercise, sleep, stress, diet, and heart rate.
<iframe src="https://fitfueltools.com/embed/biological-age-calculator" width="100%" height="600" frameborder="0" style="border-radius:12px;border:1px solid #e5e7eb;" title="Biological Age Calculator — FitFuel Tools" loading="lazy"></iframe>
GLP-1 Nutrition Calculator
Adjusted protein, calorie, and micronutrient targets for Ozempic, Wegovy, Mounjaro and Zepbound users. Prevent muscle loss on GLP-1 medications.
<iframe src="https://fitfueltools.com/embed/glp1-calculator" width="100%" height="600" frameborder="0" style="border-radius:12px;border:1px solid #e5e7eb;" title="GLP-1 Nutrition Calculator — FitFuel Tools" loading="lazy"></iframe>
Frequently asked questions
Is this really free?
Yes. All embeddable calculators are free to use on any website, forever. We do not charge for embed usage or add paywalls.
Will the calculator always work?
Yes. The iframe loads from fitfueltools.com, so your visitors always get the latest version automatically. You never need to update your code.
Can I customise the appearance?
You can control the width and height of the iframe. For deeper customisation or white-label versions, contact us.
Do I need to attribute FitFuel Tools?
The calculator includes a small 'Powered by FitFuel Tools' link. This is how we keep the service free — it sends a small amount of traffic back to us.
Does it work on WordPress?
Yes. Paste the embed code directly into an HTML block in Gutenberg, or any page builder that supports custom HTML.