Methodology
How we calculate—and where estimates stop.
Each tool applies a named method to the values you enter and returns an estimate with plain-language context. Personal and business inputs never leave the page.
Source policy
We prefer original research, government and public-health organizations, and maintained reference datasets. Every calculator links to its primary source or to the relevant methodology note.
Units and rounding
Metric values are used internally. Imperial inputs are converted before calculation, and display values are rounded only after the equation runs. Small display differences may occur because of rounding.
Body composition
BMI uses weight divided by height squared. Lean body mass uses the Boer equation. Tape and skinfold body-fat methods are population-specific and depend strongly on measurement technique; methods that cannot represent the selected population should not be used as universal guidance.
Reference weight
The Robinson equation produces a reference value from height and sex used by the formula. The displayed range is context, not a target or medical recommendation.
Calories and macros
Mifflin–St Jeor is used for resting-energy estimates. TDEE applies an activity factor. Macro results distribute a calorie target entered by the user; they do not silently infer a prescription from body weight.
Coach business calculators
Business tools use only the assumptions entered in the browser. Pricing combines allocated fixed costs, variable costs, retained revenue, and target income or margin. Capacity uses the lowest trainer, room, or concurrent-session limit. Break-even divides remaining fixed costs by contribution margin per delivered session. Missed-session loss models use stated cancellation, recovery, policy, trainer payout, and administrative-cost assumptions.
Formula register
Each entry records the method, supported population, assumptions, limitations, sources, and stable review date used by the product.
BMI Calculator
Method: Weight divided by height squared.
Supported population: Adults age 20 and older; children require age- and sex-specific percentiles.
Assumptions: Weight and height are measured consistently; Adult BMI category thresholds are appropriate for the user.
Limitations: BMI is a screening measure and does not distinguish muscle, fat, pregnancy, age-related change, or individual health status.
Reviewed: 2026-07-16
Body Fat Calculator
Method: U.S. Navy circumference and selected skinfold equations.
Supported population: Adults matching the sex, age, and measurement population supported by the selected equation.
Assumptions: Measurement sites follow the source protocol; Skinfold equations are used only for supported sex and age groups.
Limitations: Tape and skinfold results are estimates. Accuracy depends heavily on measurement technique and the population used to create each equation.
Reviewed: 2026-07-16
Waist-to-Hip Ratio Calculator
Method: Waist circumference divided by hip circumference.
Supported population: Adults using WHO measurement guidance.
Assumptions: Waist and hip use the same unit; Both circumferences are measured at standardized sites.
Limitations: This ratio is a screening indicator, not a diagnosis. Measurement placement can materially change the result.
Reviewed: 2026-07-16
Lean Body Mass Calculator
Method: Boer lean body mass equation.
Supported population: Adults within the body-size range represented by the Boer equation.
Assumptions: Height and weight are current; The selected sex-specific equation is appropriate.
Limitations: The result is a population-based estimate and is not a substitute for DEXA or another direct body-composition assessment.
Reviewed: 2026-07-16
Ideal Weight Calculator
Method: Robinson ideal body weight equation.
Supported population: Adults at least 152.4 cm tall.
Assumptions: Height-based reference weight is useful only as broad context; Body composition and health are not represented.
Limitations: No single ideal weight applies to everyone. Body composition, health, age, and personal context matter.
Reviewed: 2026-07-16
BMR Calculator
Method: Mifflin–St Jeor resting energy equation.
Supported population: Adults age 18 to 100 using the equation's sex-specific constant.
Assumptions: Weight is stable and measured in kilograms; The population equation is an appropriate estimate.
Limitations: BMR is an estimate and is lower than total daily calorie use because it excludes normal activity.
Reviewed: 2026-07-16
Resting Energy Calculator
Method: Mifflin–St Jeor resting energy equation.
Supported population: Adults age 18 to 100 using the equation's sex-specific constant.
Assumptions: The result represents resting use only; The displayed range is context, not a measured confidence interval.
Limitations: Resting energy is not a daily intake recommendation and varies with body composition and health status.
Reviewed: 2026-07-16
TDEE Calculator
Method: Mifflin–St Jeor estimate multiplied by an activity factor.
Supported population: Adults age 18 to 100 whose typical activity resembles one listed multiplier.
Assumptions: The chosen multiplier represents a typical week; Resting energy is reasonably estimated by Mifflin–St Jeor.
Limitations: Activity factors are broad estimates. Real energy expenditure can differ substantially from the result.
Reviewed: 2026-07-16
Macro Split Calculator
Method: User-provided calories distributed by the selected macro split.
Supported population: Adults using a calorie target established separately.
Assumptions: The calorie target is intentional; Four kcal per gram for protein/carbohydrate and nine for fat.
Limitations: Macro splits are planning examples, not individualized nutrition prescriptions.
Reviewed: 2026-07-16
Water Intake Calculator
Method: Weight-based estimate adjusted for activity and climate.
Supported population: Generally healthy adults without fluid restrictions or unusual hydration needs.
Assumptions: Thirty milliliters per kilogram is a planning baseline; Activity and climate multipliers are broad categories.
Limitations: Hydration needs vary with diet, health, pregnancy, medication, weather, and exercise. This is general guidance only.
Reviewed: 2026-07-16
Calorie Burn Calculator
Method: MET value multiplied by body weight and duration.
Supported population: Adults performing an activity close to the selected Compendium intensity.
Assumptions: The selected MET reflects actual intensity; Duration and weight are measured consistently.
Limitations: MET values describe population averages and may not reflect your pace, fitness, efficiency, or conditions.
Reviewed: 2026-07-16
Maximum Heart Rate Calculator
Method: Tanaka age-predicted maximum heart rate equation.
Supported population: Adults age 18 to 100 without a condition or medication that changes heart-rate response.
Assumptions: Age is the only predictor used; Percentage zones are general training bands.
Limitations: Age-based formulas can differ from measured maximum heart rate. Medication and health conditions can also alter response.
Reviewed: 2026-07-16
Bedtime Calculator
Method: Bedtime options based on 90-minute planning intervals.
Supported population: Adults planning bedtime from a preferred wake-up time.
Assumptions: Fifteen minutes is allowed to fall asleep; Ninety minutes is used as a simplified cycle interval.
Limitations: Sleep cycles are not exactly 90 minutes for every person or every night. Prioritize sufficient total sleep over exact cycle timing.
Reviewed: 2026-07-16
Personal Training Package Pricing Calculator
Method: Cost allocation, retained-revenue pricing, and target-margin calculation.
Supported population: Personal trainers, coaches, Pilates studios, fitness studios, and gym owners using their own operating assumptions.
Assumptions: Expected completed sessions represent a typical month; Tax and payment fees are entered as revenue percentages; Prices are planning estimates, not a market benchmark.
Limitations: This calculator cannot account for local demand, competitor positioning, sales conversion, or every tax obligation. Review the final price with a qualified adviser when appropriate.
Reviewed: 2026-07-16
Personal Trainer Earnings Calculator
Method: Selected compensation model applied to completed and missed-session payouts.
Supported population: Personal trainers, coaches, Pilates studios, fitness studios, and gym owners using their own operating assumptions.
Assumptions: Completed sessions earn the selected model payout; Cancellation and unattended payout inputs are flat amounts; Business margin shown is before other overhead.
Limitations: The margin shown only accounts for trainer payout. It does not include rent, taxes, payment fees, software, or other business costs.
Reviewed: 2026-07-16
Individual vs Group Training Profit Calculator
Method: Per-session revenue and cost comparison with a group attendance break-even threshold.
Supported population: Personal trainers, coaches, Pilates studios, fitness studios, and gym owners using their own operating assumptions.
Assumptions: Monthly projections use 52 ÷ 12 weeks; Each group participant pays the same price; Trainer and facility costs are incurred once per group session.
Limitations: The comparison does not account for demand uncertainty, client retention, marketing cost, or the qualitative value of different session formats.
Reviewed: 2026-07-16
Personal Trainer and Studio Capacity Calculator
Method: Time-slot capacity limited by trainers, rooms, and simultaneous-session availability.
Supported population: Personal trainers, coaches, Pilates studios, fitness studios, and gym owners using their own operating assumptions.
Assumptions: Every session requires both a trainer and an available space; Target utilization is applied after theoretical capacity; Cancellations reduce completed sessions, not physical scheduling slots.
Limitations: This is a planning model. It does not account for split shifts, staff skills, holidays, demand by time of day, or irregular operating schedules.
Reviewed: 2026-07-16
Fitness Studio No-Show Cost Calculator
Method: Missed-session revenue minus recovery methods, plus related trainer and administrative costs.
Supported population: Personal trainers, coaches, Pilates studios, fitness studios, and gym owners using their own operating assumptions.
Assumptions: Late cancellations and unattended sessions are separate rates; Rescheduling applies to late cancellations only; Cancellation fees are collected only from policy-protected late cancellations.
Limitations: Actual recovery depends on your policy, collection rate, client behavior, and whether a released slot can be resold. This estimate cannot predict those outcomes.
Reviewed: 2026-07-16
Personal Trainer and Fitness Studio Break-Even Calculator
Method: Contribution-margin break-even analysis using fixed costs, non-session revenue, session mix, and variable costs.
Supported population: Personal trainers, coaches, Pilates studios, fitness studios, and gym owners using their own operating assumptions.
Assumptions: Session mix totals 100%; Each delivered session earns the weighted average revenue; Expected session volume represents completed sessions.
Limitations: Break-even is a planning view, not a cash-flow forecast. It does not model timing of payments, debt, taxes, client churn, or seasonal demand.
Reviewed: 2026-07-16
Review cycle
Content and equations are reviewed when a source changes, a calculation issue is reported, or a material product update is released. The latest review date appears on every calculator.