Free Health Tools & Calculators
Browse 235+ free interactive health calculators, estimators, and utilities. 100% free, private, and runs directly in your browser without signup.
Doppler Echo Cardiac Output Calculator — Stroke Volume, CO & Cardiac Index
Calculate stroke volume (SV), cardiac output (CO), and cardiac index (CI) from LVOT diameter, Doppler VTI, and heart rate. With formula breakdown and worked examples. Educational tool.
IV Drip Rate Calculator — mL/hr to Drops/min (gtt/min)
Free IV drip rate calculator (also works as an IV flow rate calculator): convert infusion volume and time to mL per hour and drops per minute (gtt/min) for 10, 15, 20 and 60 gtt/mL drip sets — or work backwards from a drip rate to mL/hr. Educational tool.
Drops Per Minute Calculator (gtt/min) — IV Drip Rate
Free drops-per-minute calculator: gtt/min = (mL × drop factor) ÷ minutes. Forward + reverse modes, full standard drop-factor table (10/15/20/60 gtt/mL), and clinical whole-drop rounding guidance. Educational tool.
Drug Half-Life Calculator — Single & Multiple Dose (Educational Estimator) — nrtechstudio.com
Free drug half-life calculator: estimate remaining drug over time, time to clear a target percentage, and multiple-dose accumulation with steady-state peak and trough. First-order model with interactive decay charts. Educational estimates only — not medical advice.
DLS Calculator — Duckworth-Lewis-Stern Revised Target & Par Score
Free Duckworth-Lewis-Stern (DLS) calculator for rain-affected cricket. Compute revised targets and par scores for ODI & T20 matches with the ICC Standard Edition resource table, interruption breakdown and G50 options.
DUDIT Drug Use Screening Test Calculator — Score & Interpret the 11-Item DUDIT
Free DUDIT calculator: answer the 11 official Drug Use Disorders Identification Test questions, get your 0–44 score with cutoff interpretation (men ≥6
Duke Treadmill Score Calculator — Exercise Stress Test Risk Stratification | nrtechstudio
Free Duke Treadmill Score calculator: compute the Duke score from exercise time, ST deviation, and angina index, with risk category, original-cohort s
Dunk Calculator: Can You Dunk a Basketball? | nrtechstudio
Can you dunk? Enter your standing reach and vertical jump to get your max touch and a verdict against the 10-foot rim. Free, private, works offline.
E-Bike Range Calculator — Estimate How Far Your Battery Goes
Free e-bike range estimator: enter battery Wh, assist level, rider weight and terrain to estimate range in km or miles plus real consumption in Wh/km.
EER Calculator (Estimated Energy Requirement) — IOM/DRI Equations | nrtechstudio
Free EER calculator using the Institute of Medicine (IOM) Dietary Reference Intake equations for adults 19+. Enter age, sex, weight, height, and activ
EORTC Bladder Cancer Risk Calculator (NMIBC) — Recurrence & Progression | nrtechstudio.com
Free EORTC bladder cancer risk calculator for non-muscle-invasive bladder cancer (NMIBC). Computes recurrence (0–17) and progression (0–23) scores fro
EPDS Calculator — Edinburgh Postnatal Depression Scale (Free Screening)
Free EPDS calculator: answer the 10 validated Edinburgh Postnatal Depression Scale questions, get your 0–30 score, cutoff band (10/13) and next-step g
Epworth Sleepiness Scale (ESS) Calculator — Free Daytime Sleepiness Test
Free Epworth Sleepiness Scale (ESS) calculator. Answer the 8-question Johns (1991) questionnaire, get your 0–24 score and normal/mild/moderate/severe
Erg Calculator — Concept2 Pace, Watts & Calories
Convert Concept2 rowing ergometer pace per 500m to watts and calories per hour with the official PM monitor formulas.
EROA Calculator — Effective Regurgitant Orifice Area (PISA Method)
Calculate effective regurgitant orifice area (EROA) from PISA measurements: EROA = (2 x pi x r squared x V_aliasing) / V_max. Includes ASE 2017 severi
Estimated Average Glucose (eAG) Calculator — A1C to mg/dL & mmol/L Converter
Free estimated average glucose (eAG) calculator: convert HbA1c (%) to eAG in mg/dL and mmol/L with the Nathan 2008 (ADAG) equation, plus reference tab
Endotracheal Tube (ETT) Size Calculator — Pediatric, Neonatal & Adult
Estimate endotracheal tube (ETT) size by age and weight: Cole formula for children (uncuffed age/4+4, cuffed age/4+3), NRP neonatal weight table, adul
Pregnancy Weight Gain Calculator — IOM Guidelines
Check whether your pregnancy weight gain is on track with the IOM 2009 guidelines: BMI-based targets, weekly rates, 40-week projections, and twin adju
Fagerström Test for Nicotine Dependence (FTND) Calculator — 6-Question Score 0–10 | nrtechstudio
Free Fagerström Test for Nicotine Dependence (FTND) calculator. Answer 6 questions, get your 0–10 nicotine dependence score, per-item breakdown, inter
False Negative Pregnancy Test Calculator — How Likely Is a Missed Detection?
Estimate the chance of a false negative pregnancy test by days past ovulation (DPO), test sensitivity (10/20/25 mIU/mL) and urine timing. Based on pub
FENa Calculator — Fractional Excretion of Sodium (Prerenal vs ATN) | nrtechstudio
Free FENa calculator: fractional excretion of sodium to help distinguish prerenal AKI from intrinsic renal injury (ATN), plus a FEUrea mode for patien
Fetal Weight Percentile Calculator — Hadlock EFW by Gestational Week
Free fetal weight percentile calculator. Enter ultrasound biometry (BPD, HC, AC, FL) and gestational age to get estimated fetal weight (Hadlock 1985), weight percentile vs the Hadlock 1991 growth standard, an interactive growth curve, and SGA/AGA/LGA screening classification.
FFMI Calculator — Fat-Free Mass Index (Raw + Normalized)
Free FFMI calculator: fat-free mass index with normalized FFMI (Kouri et al. 1995), visual gauge, research-backed categories, and a built-in US Navy body-fat estimator. Private — runs entirely in your browser.
FIB-4 Calculator — Fibrosis-4 Score with Age-Adjusted Interpretation
Free FIB-4 calculator: compute the Fibrosis-4 score from age, AST, ALT and platelet count (Sterling et al. 2006). Automatic age-adjusted cutoffs (1.30 / 2.00 / 2.67), unit handling, worked example and FIB-4 vs APRI comparison. Educational screening aid — not medical advice.
Finnegan NAS Score Calculator — Neonatal Abstinence Scoring System | nrtechstudio.com
Free Finnegan Neonatal Abstinence Syndrome (NAS) score calculator: 21-item scoring checklist (Finnegan et al. 1975) with weights, interpretation bands
Fish Mercury Calculator — Check Mercury Exposure From Fish
Free fish mercury calculator: estimate your weekly methylmercury intake from 43 fish using FDA/EPA average mercury levels, compare it to the EPA reference dose for your body weight, and see safe servi
Fish Oil Dosage for Cats Calculator — EPA+DHA by Weight, Label Decoder & Chart
Free fish oil dosage calculator for cats: enter weight + your product
Flight Emissions Calculator — Estimate Your Flight's CO2
Estimate CO2 emissions for any flight: enter origin and destination (or distance), cabin class, and round trip to get kg CO2 with car, tree, and home-electricity equivalents plus an offset cost estima
Frailty Index Calculator (Rockwood 40-Item) — Deficit Accumulation Score
Free frailty index calculator based on the Rockwood deficit-accumulation model. Answer 40 items across 4 domains, get your frailty score, screening category (fit / pre-frail / frail), and a per-domain breakdown — with context for surgery planning. Educational screening aid, not medical advice.
Framingham Risk Calculator — 10-Year CVD, CHD & Stroke Score
Free Framingham risk calculator: 10-year General CVD risk (D'Agostino 2008), hard CHD risk (ATP III) and stroke risk (Framingham Stroke Risk Profile, 1991) in one tool — with points breakdown, risk categories and heart age. 100% in-browser. Educational estimate, not medical advice.
GAA Calculator — Goals Against Average & Save Percentage (Goalie Stats)
Free goals against average (GAA) calculator for goalies in soccer, ice hockey, lacrosse and field hockey. Plus a save percentage calculator. 100% client-side.
GAD-7 Anxiety Test & Scoring Calculator | Free Online
Free GAD-7 generalized anxiety disorder test: answer 7 questions, get your score (0-21), severity band, and what to do next. Screening tool, not a dia
Gastric Sleeve Weight Loss Calculator — %EWL, Monthly Projection & BMI Milestones
Gastric sleeve weight loss calculator: enter starting weight and height to see your %EWL, a month-by-month gastric sleeve weight loss projection with a typical p25–p75 range, BMI trajectory and milestones. Educational only — not medical advice.
GDU Calculator – Growing Degree Units (GDD) for Crops
Free GDU / growing degree days calculator for corn, soybean, wheat, alfalfa, sorghum and cotton. Accumulate daily heat units, track growth stages (emergence, V6, tasseling, silking, black layer) and f
Geriatric BMI Calculator (65+) — Senior BMI Cutoffs, Chart & Healthy Range
Free geriatric BMI calculator for adults 65+. Uses senior-specific cutoffs verified against ESPEN/GLIM guidelines: underweight below 23, normal 23–30, overweight 30+. Compare vs standard adult BMI, see your healthy weight range, and learn about sarcopenia and the obesity paradox.
Gestation Calculator — Animal Due Date & Pregnancy Countdown | nrtechstudio.com
Free multi-species animal gestation calculator: pick a species and enter the breeding date to get the due-date window and pregnancy countdown for dogs
Gestational Age Calculator — How Many Weeks Pregnant Am I?
Free gestational age calculator: enter your LMP, conception date, ultrasound CRL, or IVF transfer date to get your current gestational age in weeks and days, estimated due date, trimester, countdown, and a visual 40-week timeline. 100% client-side.
Glycemic Load Calculator — GI, GL & Meal Builder | nrtechstudio
Free glycemic load (GL) calculator: GL = GI x carbs / 100. 42-food GI database, meal GL builder, and GL vs GI explainer with classification bands.
Gorlin Formula Calculator — Aortic & Mitral Valve Area + Hakki
Free Gorlin formula calculator: estimate aortic valve area (AVA) and mitral valve area (MVA) from cardiac catheterization data, plus the Hakki shortcut, guideline-based stenosis classification, variable explanations, and worked cath-lab examples. Educational only — not medical advice.
Gout Diagnosis Calculator — ACR/EULAR 2015 Classification Scorer (Free)
Free gout classification calculator using the 2015 ACR/EULAR criteria (Neogi et al.): score joint pattern, episode characteristics, time course, tophu
Grain Bin Calculator — Capacity in Bushels, Pounds & Tons
Free grain bin calculator: enter bin diameter and height (round) or length, width and height (rectangular) to get storage capacity in bushels, pounds, US tons and metric tonnes for corn, wheat, soybea
Grain Conversion Calculator — Bushels, Pounds, Tons, Prices & Moisture Shrink
Free grain conversion calculator: convert bushels to pounds, kg, metric tons and short tons for corn, wheat, soybeans, oats and 6 more grains; convert between grains, convert $/bushel prices, and calc
HAS-BLED Score Calculator — Bleeding Risk Estimator for AFib (Educational) — NR Tech Studio
Free HAS-BLED calculator: estimate 1-year major-bleeding risk on anticoagulation from 9 clinical factors, with cohort bleeding rates per score, modifiable-factor checklist, and HAS-BLED vs CHA2DS2-VASc pairing guidance. Educational tool — not medical advice.
hCG Levels Calculator — Check by Week & Doubling Time
Check your hCG level against weekly reference ranges (weeks 3–40), compute hCG doubling time from two serial blood draws, and view the full hCG refere
Head Percentile Calculator — Baby Head Circumference-for-Age (WHO 0–5 Years)
Free baby head percentile calculator: enter your child's age, sex and head circumference to get the WHO head circumference-for-age percentile, z-score, growth curve and plain-language interpretation. Educational — not medical advice.
HOMA-IR Calculator — Insulin Resistance Score + QUICKI
Free HOMA-IR calculator (Matthews et al. 1985): estimate insulin resistance from fasting insulin and glucose, plus QUICKI (Katz et al. 2000), HOMA-β, automatic mg/dL ↔ mmol/L and pmol/L ↔ µU/mL conversion, interpretation ranges and a worked example. Educational — not medical advice.
Hydroxychloroquine Dose Calculator by Weight | HCQ Max Dose (AAO 5 mg/kg)
Educational hydroxychloroquine dose calculator: estimates the AAO 2016 ophthalmology safety ceiling of 5 mg/kg/day of actual body weight, checks a current dose against it, and shows 200 mg tablet schedules plus eye-screening context. Not medical advice.
Ibuprofen Dosage Calculator (200 mg Tablets & Children's Weight-Based)
Educational ibuprofen (Advil/Motrin) dose estimator: adult 200 mg tablet schedule with 24-hour counter, children's weight-based dose (10 mg/kg, suspen
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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.