Health & Wellness Calculators — Free Tools for Nutrition, Sleep, Fertility & Digital Wellness 2026
OmniCalculator has 200+ health calculators. GetHealthyCalculators has 117. MyFitnessPal has an entire app. If what you need is a blood pressure reference chart or a dialysis efficiency score, those platforms serve you well.
If what you need is to know when your fertile window opens, how much protein actually supports your training, what time to go to sleep to wake up without an alarm feeling rested, or what a dopamine detox plan looks like for your specific screen habits — these eight tools were built for those specific decisions. No account. No app download. No subscription.
All Free Health & Wellness Calculators
Calorie Deficit Calculator — Weight Loss Math Without the Guesswork
Weight loss is determined by one equation: calories consumed minus calories burned. The calorie deficit calculator establishes your TDEE (Total Daily Energy Expenditure) using the Mifflin-St Jeor equation — the formula the American Dietetic Association recognises as the most accurate predictor of resting metabolic rate — then subtracts your target deficit to produce a daily calorie target for your weight loss goal.
What the calorie deficit calculator shows:
- BMR (Basal Metabolic Rate): calories burned at complete rest
- TDEE: BMR adjusted for your activity level (sedentary to very active)
- Target daily calories for your specified weight loss rate
- Estimated weeks to goal weight at your chosen deficit
- Macronutrient split (protein, carbohydrate, fat) at the target calorie level
The deficit that produces safe, sustainable weight loss: A 500 calorie/day deficit produces approximately 0.5kg (1lb) of weight loss per week. A 1,000 calorie/day deficit produces approximately 1kg (2lb)/week — the upper limit most dietitians recommend for sustainable loss without significant muscle loss. The calculator flags when a target calorie level falls below 1,200 calories/day (women) or 1,500 calories/day (men) — the minimum for meeting basic micronutrient needs.
Why TDEE matters more than BMR: Most calorie calculators show BMR — the calories your body burns at rest — without adjusting for actual activity. A sedentary office worker and a construction labourer with identical BMRs have completely different calorie needs. The activity multiplier in the calorie deficit calculator adjusts for this, producing a TDEE that reflects your real daily energy output.
Sleep Calculator — Wake Up Without an Alarm Using Sleep Cycles
Sleep architecture follows 90-minute cycles — each cycle moving through light sleep, deep sleep, and REM. Waking in the middle of a deep sleep cycle produces the groggy, disoriented feeling most people call “not a morning person.” Waking at the natural end of a 90-minute cycle — when you’re already in light sleep — produces the alert, rested feeling that makes mornings functional.
The sleep calculator works two ways: enter your target wake time to find what time you should go to sleep, or enter your bedtime to find the ideal wake-up times — always calculated to complete full sleep cycles rather than cutting one short.
What the sleep calculator shows:
- Optimal bedtimes based on your target wake time (5, 6, 7, 8 sleep cycles)
- Optimal wake times based on your target bedtime
- Hours of sleep per option — with the 7–9 hour recommended range highlighted
- Average time to fall asleep factored in (approximately 14 minutes for most adults)
- Sleep quality notes: REM increases in later cycles, deep sleep dominates early cycles
The science behind the 90-minute cycle: A typical night of 7.5 hours covers 5 complete sleep cycles. The first two cycles are deep-sleep dominant — critical for physical recovery, immune function, and memory consolidation. The later cycles shift toward REM — where emotional processing and creative problem-solving occur. Both are necessary. Consistently sleeping 6 hours cuts the later REM cycles; consistently sleeping 9+ hours overshoots into lighter sleep stages that leave many people feeling worse.
Ovulation Calculator — Fertile Window & Cycle Tracking
Ovulation typically occurs 12–16 days before the next menstrual period — not necessarily on day 14 of the cycle. For anyone with a cycle longer or shorter than 28 days, the textbook “day 14 ovulation” is wrong for their body. The ovulation calculator identifies your personal fertile window based on your actual average cycle length and the date of your last period.
What the ovulation calculator shows:
- Estimated ovulation date based on your cycle length
- Fertile window: the 5–6 day window when conception is possible (peak fertility is the 2 days before and the day of ovulation)
- Next expected period date
- Cycle phase breakdown: menstrual, follicular, ovulation, luteal
- Conception probability by day within the fertile window
Two uses — conception and avoidance: The ovulation calculator is used by both those trying to conceive (to identify peak fertility days) and those tracking cycles for natural family planning. For medical-grade fertility tracking, basal body temperature charting and LH surge testing provide real-time confirmation that complements the calendar-based estimate this calculator produces.
Irregular cycles: The calculator works best with regular cycles (within ±2 days of your average). For significantly irregular cycles (more than 5 days variation), the fertile window estimate widens accordingly. Consult a healthcare provider if cycles vary by more than 7–10 days, as this may indicate an underlying hormonal condition worth investigating.
Protein Calculator — Daily Intake for Your Goal and Training Style
Protein intake recommendations vary by goal, training intensity, age, and body composition. The generic “0.8g per kilogram” RDA is a minimum to prevent deficiency — not an optimal intake for anyone with fitness or body composition goals. The protein calculator applies the evidence-based ranges used by sports nutritionists to produce a daily target specific to your goal.
Evidence-based protein targets by goal (2026):
| Goal | Protein Range | Notes |
|---|---|---|
| Sedentary adult (maintenance) | 0.8–1.0g/kg | RDA minimum — sufficient for non-exercisers |
| General fitness | 1.2–1.6g/kg | Supports muscle maintenance with regular exercise |
| Muscle building | 1.6–2.2g/kg | Upper range supported by meta-analysis evidence |
| Fat loss (preserving muscle) | 1.8–2.4g/kg | Higher protein during caloric deficit reduces muscle loss |
| Endurance training | 1.4–1.7g/kg | Accounts for protein catabolism during long sessions |
| Older adults (65+) | 1.2–1.5g/kg | Higher intake combats age-related muscle loss (sarcopenia) |
What the protein calculator shows:
- Daily protein target in grams based on your weight and goal
- Protein per meal if distributed across 3–5 meals (leucine threshold is better met with ≥25–30g per meal)
- Calorie contribution from protein at your target intake
- Common food sources with protein per serving for practical meal planning
Dopamine Detox Planner — Digital Wellness Reset
A dopamine detox is a structured period of reduced exposure to high-stimulation activities — social media, gaming, news feeds, streaming — that desensitise the brain’s reward system and reduce compulsive behaviour patterns. It is not about eliminating all pleasure; it is about resetting the baseline so that low-stimulation activities (reading, conversation, walking, focused work) produce satisfaction again.
What the dopamine detox planner shows:
- Screen time input by activity type (social media, gaming, news, streaming, email)
- Stimulation score: high-dopamine activities ranked by impact
- Custom detox protocol: which activities to remove, reduce, or replace
- Structured timeline: 24-hour reset, 7-day mild detox, or 30-day reset plan
- Replacement activity suggestions calibrated to your specific high-stimulation habits
- Expected timeline for baseline reset by detox intensity
Who benefits from a dopamine detox: Anyone experiencing difficulty concentrating on single tasks, finding previously enjoyable activities boring, reflexively checking their phone during conversations, or feeling anxious without device access. These are behavioural patterns that respond well to structured reduction periods — not clinical addiction, but habits that measurably impair focus and wellbeing.
The evidence base: The term “dopamine detox” is popularised neuroscience — the underlying mechanism involves neuroadaptation to chronic high-dopamine stimulation, which raises the threshold required to trigger reward responses. Structured reduction periods allow baseline sensitivity to recover. The planner applies a realistic, evidence-aligned approach rather than the extreme “no pleasure for 24 hours” version circulated on social media.
Therapy Billing Calculator — Session Rates & Insurance Reimbursement Estimates
Mental health practitioners — therapists, psychologists, counsellors, social workers — face complex billing decisions: what to charge private pay clients, how CPT codes translate to insurance reimbursements, and how to structure sliding scale fees for income-based access. The therapy billing calculator provides reference rates and billing structure guidance for private practice practitioners.
What the therapy billing calculator covers:
- Standard session CPT codes: 90834 (45 min), 90837 (60 min), 90847 (couples/family)
- Insurance reimbursement benchmarks by payer type (Medicare, Medicaid, major commercial insurers)
- Private pay rate guidelines by credential level and market
- Sliding scale fee structure: income-based tiers that maintain practice sustainability
- Session volume and revenue modelling for private practice planning
Why therapy billing requires a dedicated tool: Standard service business billing tools don’t account for CPT code structures, insurance reimbursement rates that bear no relationship to private market rates, or the ethics of sliding scale access. This calculator is designed for practitioners, not patients — it addresses the business side of running a sustainable mental health practice.
BAC Calculator — Blood Alcohol Content Estimate (Widmark Formula)
The BAC calculator estimates blood alcohol content using the Widmark formula — the standard forensic method used by researchers and law enforcement for BAC estimation. Enter your weight, sex, number of standard drinks consumed, type of alcohol, and hours since drinking began. The result is an estimated BAC level with a severity indicator and approximate time to reach 0.00%.
What the BAC calculator shows:
- Estimated current BAC using the Widmark formula
- BAC severity: sub-threshold, impaired (0.05%+), illegal to drive (0.08%+ in most US states), dangerously impaired (0.15%+)
- Approximate time until BAC returns to 0.00% (liver processes approximately 0.015% per hour)
- Standard drinks visualiser — showing what counts as one standard drink by beverage type
Legal limits by jurisdiction:
- United States: 0.08% (federal standard; Utah: 0.05%)
- United Kingdom: 0.08% (England, Wales, NI); 0.05% (Scotland)
- Australia: 0.05% (national)
- Canada: 0.08% (criminal; provincial administrative limits at 0.05%)
- Most of Europe: 0.05%
This calculator is a planning and education tool, not a substitution for a breathalyser. Factors including food intake, individual metabolism, medications, fatigue, and hydration status affect actual BAC in ways the formula cannot fully account for. The estimate indicates general impairment risk — not a definitive sobriety clearance.
How These Tools Work Together for Common Health Goals
Goal: Lose Weight Sustainably
- Calorie Deficit Calculator — establish TDEE and daily calorie target
- Protein Calculator — set protein minimum to preserve muscle during deficit (1.8–2.4g/kg)
- Sleep Calculator — optimise sleep timing (sleep deprivation increases ghrelin, reduces leptin, directly undermining calorie control)
Goal: Improve Focus and Productivity
- Dopamine Detox Planner — identify high-stimulation habits impairing attention
- Sleep Calculator — ensure you’re completing full sleep cycles (REM supports cognitive performance)
Goal: Family Planning
- Ovulation Calculator — identify your personal fertile window based on actual cycle length
- Calorie Deficit Calculator — ensure adequate nutrition during conception attempts (caloric restriction during this period has documented effects on cycle regularity)
Goal: Build Muscle
- Protein Calculator — confirm 1.6–2.2g/kg daily intake
- Calorie Deficit Calculator — check you’re in a caloric surplus (muscle building requires energy above maintenance)
- Sleep Calculator — growth hormone is primarily secreted during deep sleep (cycles 1–2)
Frequently Asked Questions
How many calories should I eat to lose weight?
The evidence-based range is a 500–750 calorie daily deficit from your TDEE, producing 0.5–0.75kg (1–1.5lb) of weight loss per week. Larger deficits (above 1,000 calories/day) accelerate weight loss but increase muscle loss, nutrient deficiency risk, and diet fatigue — making long-term adherence difficult. The calorie deficit calculator establishes your personal TDEE using the Mifflin-St Jeor equation and outputs a daily calorie target for your chosen rate of loss.
How does the sleep calculator determine the best wake times?
The sleep calculator works backward from your target wake time in 90-minute increments — each representing one complete sleep cycle. Adding approximately 14 minutes to fall asleep, the calculator identifies the bedtimes that allow you to complete 5, 6, 7, or 8 full cycles before your alarm. Waking at the end of a cycle (during light sleep) rather than the middle of one (during deep sleep) significantly reduces sleep inertia — the groggy feeling that persists for 20–60 minutes after an ill-timed alarm.
When is my fertile window?
Your fertile window is typically 5–6 days long, ending on ovulation day. Sperm survive 3–5 days in the reproductive tract; the egg is viable for 12–24 hours after ovulation. The two days before ovulation and the day of ovulation are peak fertility days. The ovulation calculator estimates your ovulation date by subtracting approximately 14 days from your expected next period — adjusting for your actual cycle length rather than assuming a standard 28-day cycle.
How much protein do I need per day?
For general fitness and body composition goals: 1.6–2.2g per kilogram of body weight. For fat loss specifically: 1.8–2.4g/kg to minimise muscle loss during a caloric deficit. For older adults: 1.2–1.5g/kg to counteract age-related muscle loss. The generic 0.8g/kg RDA is a deficiency-prevention minimum — insufficient for anyone exercising regularly. The protein calculator applies your weight and goal to produce a daily gram target and per-meal distribution guidance.
What is a dopamine detox and does it work?
A dopamine detox is a structured reduction of high-stimulation activities — social media, gaming, streaming, news feeds — to reset the brain’s reward sensitivity. The underlying mechanism is neuroadaptation: chronic exposure to high-dopamine activities raises the stimulation threshold required to trigger reward responses, making lower-stimulation activities feel less satisfying. Reducing high-stimulation input allows baseline sensitivity to recover over days to weeks. The evidence supports structured digital reduction for improving attention and reducing compulsive phone-checking behaviour. The extreme version (no pleasure of any kind for 24 hours) has no scientific basis and is not what this planner implements.
What is the legal BAC limit for driving?
In most US states, 0.08% BAC is the legal limit for driving under the influence. Utah’s limit is 0.05%. Scotland’s limit is 0.05%. Most European countries set the limit at 0.05%. Australia and Canada use 0.05% as the administrative limit with criminal charges above 0.08%. The BAC calculator shows your estimated level alongside the legal thresholds for your jurisdiction — but is not a substitute for a calibrated breathalyser for actual sobriety decisions.
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