Free Health Tools & Calculators
Browse 235+ free interactive health calculators, estimators, and utilities. 100% free, private, and runs directly in your browser without signup.
BMI Calculator — Body Mass Index (Metric & Imperial) | nrtechstudio.com
Free BMI calculator with metric & imperial units. Get your Body Mass Index, WHO weight category, visual gauge, healthy weight range for your height, BMI Prime and Ponderal Index. Private — 100% in your browser.
BMI Calculator for Men — BMI, Body Fat % & Ideal Weight
Free BMI calculator for men: computes BMI, WHO category, ideal weight range, and estimated body fat percentage (Deurenberg formula for men). 100% client-side.
Child BMI Percentile Calculator (CDC, Ages 2–20)
Free child BMI percentile calculator using the CDC BMI-for-age LMS method (ages 2–20, boys & girls). Get BMI, percentile, z-score and CDC weight-status screening category.
BMI Weight Loss Calculator — Plan Your Calorie Deficit Safely
Plan weight loss from your BMI: enter height, current weight and target weight or BMI target plus a timeframe in weeks. Get the daily calorie deficit you need, a weekly projection timeline, TDEE context, and safety flags for unsafe deficits.
BMR Calculator — Mifflin-St Jeor + TDEE
Free BMR calculator using the Mifflin-St Jeor equation (men & women) with Harris-Benedict (revised) comparison, 5 activity-level TDEE, and lose / maintain / gain calorie targets. 100% client-side, educational.
Harris-Benedict BMR Calculator: Original 1919 vs Revised 1984 Equation
Free Harris-Benedict BMR calculator showing both the original 1919 and the revised 1984 (Roza-Shizgal) equations side by side, with step-by-step breakdown, history, and Mifflin-St Jeor comparison.
BODE Index Calculator — COPD Prognosis Score
BODE Index (Body mass, Obstruction, Dyspnea, Exercise) 0–10 calculator for COPD based on Celli et al. 2004. Compute score + quartile free.
Body Fat Calculator — US Navy, Skinfold & BMI Methods | nrtechstudio.com
Free body fat percentage calculator with 3 methods side-by-side: US Navy tape method, Jackson-Pollock 3-site skinfold and BMI-based estimate. See your ACE category, fat vs lean mass, and how to measure.
Body Frame Size Calculator — Small, Medium or Large Frame (Wrist Method)
Free body frame size calculator: enter your height and wrist circumference to find whether you have a small, medium, or large body frame. Classic height-vs-wrist chart for men and women, full reference table, worked examples and FAQ.
Bowling Average Calculator — 10-Pin Average & League Handicap | NR Tech Studio
Free bowling average calculator: enter your 10-pin game scores to get your average, series total, high game, and league handicap (220 basis, 90% default, adjustable).
Breast Cancer Recurrence Risk Estimator (Educational) — NR Tech Studio
Free educational estimator that scores commonly-discussed breast cancer tumor factors (stage, grade, nodes, size, hormone status, HER2) on an illustrative 0–100 scale. Not a clinical prediction — validated tools like PREDICT and Oncotype DX are used by doctors.
Breast Cancer Risk Estimator — 5-Year & Lifetime (Simplified Gail Model)
Educational breast cancer risk estimator based on a simplified Gail model (BCRAT): 5-year and lifetime risk from age, age at menarche, age at first birth, family history, and breast biopsies. Estimate only — not medical advice.
Breastfeeding Calorie Calculator — Daily Calorie Needs While Nursing
Estimate how many calories you need while breastfeeding: BMR (Mifflin-St Jeor) + activity + IOM lactation allowance (330 kcal/day for months 0-6, 400 kcal/day for months 7-12), with an optional safe weight-loss target.
Bulb Spacing Calculator — How Many Bulbs to Plant & How Deep | nrtechstudio
Free bulb spacing calculator: pick a bulb type, enter your bed size, and get exact planting distance, depth, and how many bulbs to buy. Grid and staggered layouts, 18 bulb types.
CAGE Questionnaire — 4-Question Alcohol Screening Calculator
Free CAGE questionnaire alcohol screening: answer the 4 official CAGE questions (Cut down, Annoyed, Guilty, Eye-opener; score 0-4, cutoff ≥2). Screeni
Calorie Calculator — Daily Calorie Needs & Macro Split
Free calorie calculator: estimate daily calorie needs with the Mifflin-St Jeor equation, 5 activity levels, and goals to lose, maintain, or gain weight — plus a simple protein, fat, and carb split.
Calorie Deficit Calculator — Daily Deficit for Weight Loss
Calculate your daily calorie deficit for weight loss: enter kg to lose and weeks to get the daily deficit, or enter a deficit to see your timeline. Safety bands 500-750 kcal/day, intake floors, weekly projection.
Calorie Density Calculator: Calories per Gram of Any Food | nrtechstudio.com
Free calorie density calculator: enter calories and weight to get calories per gram, the Volumetrics category (very low, low, medium, high), compare t
Calories Burned Calculator — MET-Based Activity Calorie Burn
Free calories burned calculator: pick an activity, enter your weight and duration, and get an estimate via MET values from the 2011 Compendium of Physical Activities. Compare two activities side by side or plan a multi-activity session.
Carb Calculator — How Many Carbs Per Day?
Free carb calculator: convert your calorie target to daily carb grams (by %, g/kg, or grams), see net carbs, per-meal breakdown, low-carb and keto thresholds. Educational tool.
Cardiac Index Calculator — CI = CO / BSA
Free cardiac index calculator: enter cardiac output plus weight and height to get BSA (DuBois or Mosteller) and cardiac index in L/min/m², with normal
Cat BMI Calculator — Feline Body Condition Score (BCS 1–9)
Free cat BMI calculator: estimate your cat
Cat Calorie Calculator — Daily kcal Needs for Cats | nrtechstudio.com
Free cat calorie calculator: find your cat
Cattle Per Acre Calculator: Stocking Rate, Carrying Capacity & AUM | nrtechstudio
Free cattle stocking rate calculator: enter acres, forage yield, cow weight and grazing days to get carrying capacity (cows per acre), acres per cow, and total AUM.
CDAI Calculator — Crohn's Disease Activity Index (Best 1976)
Free CDAI calculator: compute the Crohn's Disease Activity Index from the 8 weighted components of Best et al. (1976) — 7-day diary, extraintestinal c
Centor Score Calculator — McIsaac Modified Centor Score for Strep Pharyngitis
Free Centor score calculator with the McIsaac age modification: 4 clinical criteria (fever ≥38°C, no cough, tonsillar exudate, tender anterior cervica
Cephalexin for Cats Dosage Calculator by Weight — mg Range Estimator, mL & FAQ
Free cephalexin for cats dosage calculator: enter your cat
Cephalexin for Dogs Dosage Calculator by Weight — mg Range Estimator, mL, Chewable Combos & FAQ
Free cephalexin for dogs dosage calculator: enter your dog
CHA2DS2-VASc Score Calculator — AFib Stroke Risk Estimator (Educational) — NR Tech Studio
Free CHA2DS2-VASc calculator: estimate stroke risk in atrial fibrillation from 8 clinical factors, with live score, breakdown, interpretation table, and worked examples. Educational tool — not medical advice.
Child BMI Calculator — CDC BMI-for-Age Percentile (Ages 2–20)
Free child BMI calculator: enter age, height and weight to get your child's BMI, CDC BMI-for-age percentile and weight category, plus parent guidance. Ages 2–20. Educational use.
Child-Pugh Score Calculator — Cirrhosis Severity (Class A/B/C)
Free Child-Pugh (Child-Turcotte-Pugh) score calculator. Enter bilirubin, albumin, INR, ascites and encephalopathy to get the 5–15 point total, Class A/B/C and published survival context. Educational tool — not medical advice.
Cholesterol Units Converter — mg/dL ↔ mmol/L (Cholesterol & Triglycerides)
Free cholesterol units converter: convert total, LDL and HDL cholesterol between mg/dL and mmol/L (divide by 38.67) and triglycerides (divide by 88.57), with general reference ranges. 100% in-browser. Estimates only — not medical advice.
CIWA-Ar Alcohol Withdrawal Score Calculator | nrtechstudio
Free CIWA-Ar (Clinical Institute Withdrawal Assessment for Alcohol, revised) calculator: score all 10 items, total 0–67, and see the severity band wit
Clomid Ovulation Calculator — Estimate Ovulation on Clomiphene
Free Clomid ovulation calculator: enter your last period date, the cycle day you started Clomid, and cycle length to estimate your ovulation window (typically 5-9 days after the last tablet), fertile window, and monitoring plan. Educational estimate only — not medical advice.
CO2 Grow Room Calculator — Dose, Flow Rate & Tank Duration
Free CO2 grow room calculator: room volume to CO2 dose (lb, ft³, grams), sealed-room flow rate (CFH), time to target ppm, tank duration, and vented-room injection rate.
Conception Calculator — Estimate Your Conception Date
Free conception date calculator. Estimate when conception happened from your due date (due − 266 days) or from your last menstrual period (LMP + 14 days), with an honest range — not just one date.
Conception Date Calculator — When Was I Conceived?
Free conception date calculator: estimate when you were conceived from a birthdate (birthdate − 266 days, ±7-day range), or estimate from a due date. Educational estimate, 100% client-side.
Cost of Smoking Calculator
Free cost of smoking calculator: daily, yearly and lifetime spend, price-rise projection, invest-it-instead growth, and smoke vs vape vs NRT comparison.
Cricket Chirp Thermometer — Estimate Temperature from Cricket Chirps (Dolbear's Law)
Free cricket chirp thermometer: count cricket chirps and estimate air temperature with Dolbear's law. Field cricket and snowy tree cricket formulas, 15-second shortcut, reverse temperature-to-chirp mo
CVD Risk Calculator — 10-Year Framingham Risk Score
Free 10-year CVD risk calculator using the Framingham General CVD Risk Score (D'Agostino 2008): enter age, cholesterol, blood pressure, smoking and diabetes to get your points, 10-year risk % and risk category. 100% in-browser. Educational tool — not medical advice.
Cycling Power Zones Calculator — FTP Zones (Coggan 7-Zone) + LTHR Heart Rate Zones
Free cycling zones calculator: enter your FTP to get all 7 Coggan power zones in watts, or enter LTHR for cycling-specific heart rate zones. 100% client-side.
Denver HIV Risk Score Calculator — Estimate Undiagnosed-HIV Risk (Haukoos 2012)
Free Denver HIV Risk Score calculator: answer 8 questions from the Haukoos et al. (2012) clinical prediction rule and get your score, risk band, and c
PHQ-9 Depression Test & Calculator — Check Your Depression Score (Free)
Free PHQ-9 depression screening calculator: answer the 9 validated PHQ-9 questions, get your 0-27 score, severity band (minimal, mild, moderate, moder
Dihybrid Cross Punnett Square Calculator — 16-Box Grid, 9:3:3:1 Ratios
Free dihybrid cross Punnett square calculator: enter two parent genotypes (AaBb x AaBb), get the 16-box grid, 9:3:3:1 phenotypic ratio, 1:2:1:2:4:2:1:2:1 genotypic ratio, and per-phenotype probabiliti
Maddrey Discriminant Function Calculator — Free Online DF Score for Alcoholic Hepatitis
Free online Maddrey discriminant function calculator: DF = 4.6 × (PT patient − PT control) + bilirubin (mg/dL). Severity threshold 32, breakdown, examples. Educational tool — not medical advice.
DNA to mRNA Converter — Transcription + Codon Translation
Free DNA to mRNA converter: transcribe a template or coding DNA strand to mRNA, translate codons to amino acids across 3 reading frames, with start/stop highlighting, GC content and sequence validatio
Dog BMI Calculator — Is My Dog Overweight? (Breed-Based Check)
Free dog BMI calculator: check if your dog is overweight by comparing its weight to the ideal range for 40+ breeds. Approximate 1-9 body condition score, multi-dog compare & puppy growth check. 100% private, runs in your browser.
Dog Water Intake Calculator — How Much Water Should Your Dog Drink?
Free dog water intake calculator: estimate your dog
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How to Use the Tools Directory
Every tool is a single interactive page: enter your inputs, get instant results, no account needed. Use the search box (shortcut: press /) to jump straight to a tool, or browse categories when you are exploring. Each card links to the tool's permanent URL, which you can bookmark or share.
Because all computation happens in your browser, the tools are fast, private, and free forever. If a result looks wrong, use the one-click report control on the tool page so it can be fixed.
Tool Categories at a Glance
| Category | What you will find | Example tasks |
|---|---|---|
| Developer | Encoders, formatters, regex, network tools | Format JSON, test regex, subnet a network |
| Finance | Tax, loans, salary, investing | Estimate tax brackets, amortize a loan |
| Home improvement | Estimators, measurements, materials | Size a wire, estimate paint or flooring |
| Health & fitness | Body metrics, nutrition, workouts | Track BMI, plan calories, score fitness tests |
| Math & science | Converters, geometry, statistics | Convert units, solve triangles |
| Text | Counters, sorters, generators | Count words, alphabetize a list |
| Color | Pickers, converters, checkers | Convert HEX to RGB, check contrast |
| Everyday life | Cooking, travel, automotive, pets | Convert recipes, plan fuel costs |
Popular Tasks and Where to Start
| I want to... | Start with | Why |
|---|---|---|
| Convert between number bases | Binary Converter | Step-by-step base conversion with charts |
| Validate and format data | JSON Formatter | Pretty-print and check JSON instantly |
| Count words for an essay | Word Counter | Words, characters, reading time |
| Check password strength | Password Strength Meter | Entropy-based strength scoring |
| Grade text readability | Readability Score | Flesch-Kincaid and grade levels |
| Audit color contrast | Accessibility Checker | WCAG contrast ratios in one click |
Tools Directory FAQ
What is the NRTechStudio tools directory?
It is a free catalog of more than 2,700 interactive web tools: calculators, converters, generators, and checkers for developers, finance, home improvement, health, education, and everyday tasks.
Are all the tools really free?
Yes. Every tool in the directory is free to use with no sign-up, no trial, and no paywall. They run entirely in your browser.
Do I need to create an account?
No. There are no accounts, logins, or subscriptions. Open a tool and use it immediately.
Is my data private when I use these tools?
Yes. The tools are 100% client-side: your inputs are processed by JavaScript in your own browser and never sent to a server.
How do I find the right tool?
Use the search box at the top of the directory (press / to focus it), or browse by category. Every tool card shows a short description of what it computes.
Do the tools work on mobile?
Yes. The directory and the tools use responsive layouts that adapt to phones, tablets, and desktops.
How many tools are there?
The directory holds more than 2,700 tools and grows regularly as new calculators and converters are published.
Can I request a new tool?
Yes. Each tool page has a report/feedback control you can use to request features or new tools; requests help prioritize what gets built next.
Are the tools accurate?
Calculators use published formulas and reference data (tax tables, NEC ampacity, standard conversions). Each tool page documents its method, and issues can be reported in one click for a fix.
Do tools work offline?
Once a tool page has loaded, most tools keep working without a connection because the logic is client-side JavaScript. The directory search needs the page loaded first.
What categories are covered?
Developer utilities, finance and tax, home improvement, health and fitness, math and science, text tools, color tools, networking, education, and everyday life calculators, among others.
Can I bookmark or share a tool?
Yes. Every tool has its own permanent URL under nrtechstudio.com/tools/, which you can bookmark or share directly.
Is there an API for these tools?
The tools are interactive web pages, not API endpoints. The underlying math is plain JavaScript you can inspect in the page source.
Why do some tools show ratings?
Ratings aggregate user feedback to surface the most trusted tools and flag pages that need fixes or better explanations.
How often are new tools added?
New tools are published on a continuous pipeline, prioritized by measured search demand and by user requests from the feedback controls.
Who builds these tools?
NRTechStudio, an independent tools studio focused on free, private, client-side utilities that respect user privacy.