Health Calculators
Clinical sources
This calculator estimates the likely ovulation day and fertile window using menstrual cycle timing. Ovulation timing varies from person to person and from cycle to cycle. This tool does not confirm ovulation or pregnancy.
- NHS, Periods and fertility in the menstrual cycle
- Mayo Clinic, How to get pregnant
- CDC, Infertility frequently asked questions
- CDC, Fertile window evidence cited in fertility research
Typical educational wording: In most menstrual cycles, ovulation occurs about 14 days before the next period. The highest chance of pregnancy is during the fertile window, which spans the 5 days before ovulation and the day of ovulation.
Clinical sources
This calculator estimates the likely ovulation day and fertile window using menstrual cycle timing. Ovulation timing varies from person to person and from cycle to cycle. This tool does not confirm ovulation or pregnancy.
- NHS, Periods and fertility in the menstrual cycle
- Mayo Clinic, How to get pregnant
- CDC, Infertility frequently asked questions
- CDC, Fertile window evidence cited in fertility research
Typical educational wording: In most menstrual cycles, ovulation occurs about 14 days before the next period. The highest chance of pregnancy is during the fertile window, which spans the 5 days before ovulation and the day of ovulation.
Clinical sources
This calculator estimates gestational age and due date using last menstrual period or conception timing. Standard clinical method uses 280 days from the first day of the last menstrual period for an average 28 day cycle. This estimate varies with cycle length and ovulation timing.
- American College of Obstetricians and Gynecologists, Pregnancy dating and fetal development
- ACOG, Estimating your due date
- NHS, Your pregnancy due date
- Centers for Disease Control and Prevention, Pregnancy information and tracking
Clinical calculation basis: gestational age starts from first day of last menstrual period. Average duration is 40 weeks or 280 days. This method assumes regular ovulation around day 14 in a 28 day cycle.
Professional Help Available
Clinical sources
This calculator estimates basal metabolic rate using validated clinical equations. Basal metabolic rate represents energy expenditure at rest under standard conditions. It is used in clinical nutrition and weight management planning. Results vary based on body composition, age, sex, and physiological state.
- Mifflin et al., 1990, A new predictive equation for resting energy expenditure in healthy individuals
- NCBI Bookshelf, Resting Energy Expenditure and clinical nutrition overview
- NCBI Bookshelf, Energy expenditure in human nutrition assessment
Most modern clinical practice uses the Mifflin St Jeor equation as the preferred estimation method for basal metabolic rate in adults.
This tool provides an estimate only. Clinical evaluation is required for medical nutrition planning.
Clinical sources
This calculator estimates daily energy needs using basal metabolic rate equations and physical activity multipliers. Results represent population-based estimates of energy expenditure. Individual needs vary with body composition, medical conditions, and metabolic differences.
- Mifflin MD et al. 1990, A new predictive equation for resting energy expenditure in healthy individuals
- FAO WHO UNU Expert Consultation, Human energy requirements 2004
- World Health Organization, Energy and protein requirements report
- Centers for Disease Control and Prevention, Healthy weight and energy balance concepts
Most modern calorie calculators use the Mifflin St Jeor equation to estimate resting energy expenditure, then apply activity multipliers to estimate total daily energy needs.
These values support general nutrition planning and do not replace clinical assessment.
Clinical sources
This calculator estimates body fat percentage using validated anthropometric prediction models. These models estimate body composition from height, weight, age, and body circumference or skinfold measurements. Results are population estimates and do not replace clinical body composition assessment methods such as DEXA.
- Mifflin et al. 1990. A new predictive equation for resting energy expenditure and related anthropometric modeling
- U.S. Department of Health and Human Services. Physical Activity Guidelines Advisory Committee Report (body composition assessment context)
- American Council on Exercise. Body fat percentage estimation and classification standards
- Hodgdon JA, Beckett MB. U.S. Navy circumference method (Naval Health Research Center model)
Common methods used in this calculator include the U.S. Navy circumference method developed by Hodgdon and Beckett, BMI-based estimation models such as the Deurenberg equation, and skinfold-based regression models such as Jackson and Pollock.
U.S. Navy method formula basis: BF% = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76 (men) and adjusted formula for women including hip circumference.
Accuracy varies across populations. Error margins are commonly reported around ±3–5% compared with DEXA measurements.
Clinical sources
This calculator uses Body Mass Index. BMI is a screening measure based on weight and height. It helps classify underweight, normal weight, overweight and obesity in adults. It does not measure body fat directly and does not diagnose disease.
BMI formula used: weight in kilograms divided by height in meters squared.
- World Health Organization, Body Mass Index overview and classification
- Centers for Disease Control and Prevention, Adult BMI calculator and interpretation
- NHS, BMI calculator and healthy weight guidance
Standard clinical interpretation uses WHO BMI categories for adults. BMI is a screening tool and does not replace clinical assessment.
Clinical sources
This calculator estimates body type tendency using anthropometric ratios such as waist, hip, shoulder, wrist, height, and weight. It is based on somatotype research and body composition assessment used in sports and clinical physiology. It does not define a medical condition or fixed category.
- Somatotype and body composition using Heath Carter method in clinical and sports assessment
- Healthline. Body types and anthropometric characteristics of ectomorph mesomorph endomorph
- MedicineNet. Somatotype classification and physical structure description
- Encyclopaedia Britannica. Somatotype classification system and historical context
The most commonly referenced model is the Heath Carter somatotype system. It uses measurements of body fat distribution, muscularity, and linearity to estimate endomorphic, mesomorphic, and ectomorphic tendencies.
Modern medical literature treats somatotypes as descriptive and not diagnostic. Body type can shift with training, nutrition, and changes in body composition.
Clinical sources
This calculator estimates ideal body weight using validated height-based equations. These equations were developed for clinical nutrition, pharmacology dosing, and population health assessment. They provide reference ranges, not individualized medical targets.
- Mifflin et al. (1990). Predictive equation for resting energy expenditure and related clinical anthropometric modeling
- FAO / WHO / UNU (2004). Human energy requirements and body weight reference standards
- U.S. Department of Health and Human Services. Physical Activity Guidelines Advisory Committee Report
- Devine formula and Ideal Body Weight equations used in clinical pharmacology (StatPearls, NCBI Bookshelf)
- Robinson, Miller, and Hamwi equations used for clinical ideal body weight estimation (StatPearls, NCBI Bookshelf)
Common clinical formulas include: Devine (1974), Robinson (1983), Miller (1983), and Hamwi (1964). These models estimate body weight from height using population-derived constants.
Ideal body weight is used in medication dosing, nutrition planning, and risk stratification. It does not replace body composition assessment such as DEXA or clinical evaluation.
The ‘Calculate your heart age’ service compares your real age to your heart age by asking you questions about your health. You’ll also find out how to improve your heart age by making some healthy lifestyle changes.
The service also highlights the importance of knowing your blood pressure and cholesterol numbers and will give a more accurate result if these numbers are acquired.
Clinical sources
This calculator is based on the Digit Span task used in neuropsychological assessment of attention and working memory. The task measures immediate recall capacity for number sequences in forward and backward order. It is widely used in clinical cognitive testing and standardized intelligence scales.
- StatPearls. Digit Span and Working Memory Assessment in Clinical Neuropsychology
- NCBI Bookshelf. Neuropsychological assessment of attention and working memory
- Wechsler Adult Intelligence Scale (WAIS-IV), Digit Span subtest description
- Working memory and digit span performance in cognitive assessment research
The Digit Span task is part of standardized neuropsychological batteries such as the WAIS. It typically includes forward recall, backward recall, and sequencing conditions to evaluate attention span and working memory manipulation.
Performance on digit span tasks is influenced by age, education, attention, fatigue, and neurological or psychiatric conditions. Results are used as screening indicators and require clinical interpretation in full assessment contexts.
References
1. Centers for disease control and prevention. Health Effects of Cigarette Smoking. National Center for Chronic Disease Prevention and Health Promotion. Accessed 2017.
2. Yanbaeva DG, Dentener MA, Creutzberg EC, Wesseling G, Wouters EF. Systemic effects of smoking. Chest. 2007; 131(5):1557-66.
Nicotine Dependence Test
Based on the validated 6-item Fagerström Test for Nicotine Dependence. The total score ranges from 0 to 10. Higher scores indicate greater nicotine dependence. :contentReference[oaicite:1]{index=1}
Result
Clinical sources
This questionnaire is based on the Fagerström Test for Nicotine Dependence (FTND). It is a standardized 6-item instrument used in clinical and research settings to assess the intensity of nicotine dependence in cigarette users. Scores are summed to produce a severity index from 0 to 10.- NIDA Clinical Trials Network. Fagerström Test for Nicotine Dependence (FTND)
- University of Wisconsin–Madison. FTND scoring and instrument description
- European Union Drugs Agency (EUDA). Fagerström Test for Nicotine Dependence overview
- CORESTA. Fagerström Test for Nicotine/Cigarette Dependence (psychometric description)
- Heatherton TF et al. (1991). The Fagerström Test for Nicotine Dependence. British Journal of Addiction
The FTND evaluates cigarette dependence using 6 items covering time to first cigarette, daily consumption, compulsive use patterns, and difficulty refraining. Higher scores indicate higher physical dependence and are used for screening and treatment planning.
Interpretation is clinical and should be combined with full medical assessment. The tool does not diagnose addiction severity alone and does not replace clinician evaluation.
