About

This site offers "FIT TOOLS", a set of free strength-training calculators for everyone who enjoys working out. From estimating your 1RM (one-rep max), to calories burned, daily protein targets, TDEE (total daily energy expenditure), and rest-interval guidance, you can use these planning tools for free, with no sign-up required.

FIT TOOLS is one of the services provided by Joy Next World (joy-next-world.com). Joy Next World also offers the Gym training-log app (currently in development), and plans to add free tools in many genres beyond strength training. Paid plans are planned for the Gym app in the future, while the FIT TOOLS calculators and guides are planned to remain free to use.

For details about the person who builds and runs this site, see the developer profile, which covers the motivation behind it, the technology stack, and the editorial policy.

• 1RM CalculatorEstimate your one-rep max (1RM) from weight and reps. Includes a %-conversion table.
• Calories Burned CalculatorEstimate calories burned from your activity and body weight (METs method).
• Protein CalculatorCalculate your daily protein target based on your goal and body weight.
• TDEE CalculatorEstimate total daily energy expenditure from basal metabolism and activity level.
• Rest Interval CalculatorShows a guideline for rest time between sets based on your goal.
• BMI CalculatorCalculate BMI, weight category and ideal weight from height and weight.
• Body Fat CalculatorEstimate body fat percentage and lean body mass (BMI and Navy methods).
• PFC / Macro CalculatorWork out your protein, fat and carbohydrate split by goal.
• Water Intake CalculatorEstimate your daily water needs from body weight and activity level.
• RPE CalculatorConvert weight, reps, and RPE into RIR and estimated 1RM.
• Plate CalculatorWork out which plates to load on the barbell for a target weight.
• FFMI CalculatorCalculate your Fat-Free Mass Index from height, weight, and body fat.
• Interval TimerCountdown for rest between sets, with an end beep and Pomodoro mode.
• Heart Rate ZonesMax heart rate and five target zones from your age.
• Running Pace CalculatorConvert distance, time and pace, with projected race times.
• Sleep Cycle CalculatorWork out the best bedtime from 90-minute sleep cycles.
• DOTS & Wilks ScoreBodyweight-adjusted strength scores (DOTS and Wilks 2020).
• Weight Change SimulatorProject your weight from calorie balance, or work back from a goal.
• Steps to CaloriesCalories burned and distance walked from your step count.
• Caffeine Intake CalculatorGuideline safe caffeine limits from your body weight.

This site strives to provide information you can use with confidence. Each calculator is designed, as far as possible, on the basis of publicly available academic findings and commonly used formulas.

All calculations run inside your browser (client-side), and the values you enter—such as body weight and age—are never sent to or stored on a server. For how we handle personal information and cookies, please see our Privacy Policy.

• Basis of our information

  The formulas and figures used in each calculator are based on academic papers and public guidelines widely referenced in sports science and nutrition. The underlying references are cited in the "Formulas & references" section on each page.

  Author and organization names in the references are shown only to cite the source; this site is not affiliated with, supervised by, or endorsed by those parties (see our Terms & Disclaimer).

• How we review content

  When the findings behind a formula are updated, or an error is found, we revise and update the content promptly. The "Last updated" date on each page is managed to reflect the actual date of revision.

• About expert supervision

  This site is operated by an individual and is not supervised by qualified professionals such as physicians or registered dietitians. Results are estimates based on general formulas, not guidance tailored to your individual health condition. If you have a pre-existing condition, are pregnant, or have any illness, please consult a physician before use.

• Feedback

  If you find an error or would like to suggest an improvement, please reach out via our Contact page. Your feedback helps us improve the content.

The results from this site are based on general formulas and are estimates only; we do not guarantee their effectiveness or accuracy. Due to individual differences in body composition, training experience, and so on, they may differ from your actual values.

The results are not a substitute for medical or nutritional advice. For decisions regarding your health or training, please consult a physician or specialist as needed. For details, see our Terms & Disclaimer.

For questions or feedback about this site, please reach out via our Contact page.