Free Health Tools & Calculators
Browse 235+ free interactive health calculators, estimators, and utilities. 100% free, private, and runs directly in your browser without signup.
ICH Volume Calculator (ABC/2) — Intracerebral Hemorrhage Volume
Free ICH volume calculator using the ABC/2 method (Kothari et al. 1996). Enter A, B, C in mm or cm, choose ABC/2, ABC/2.3 or ABC/3, get hemorrhage volume in mL. Educational estimate — not medical advice.
Ideal Body Weight (IBW) Calculator — Devine, Robinson, Miller & Hamwi | nrtechstudio.com
Free ideal body weight (IBW) calculator: compares the 4 classic formulas — Devine (1974), Robinson (1983), Miller (1983) and Hamwi (1964) — plus BMI h
IIFYM Macro Calculator — Protein, Carbs & Fat Targets
Free IIFYM macro calculator: estimate your TDEE with Mifflin-St Jeor, pick cut, maintain or bulk, then get adjustable protein, fat and carb targets in grams and % of calories — plus a meal split table.
Implantation Calculator — Estimate Your Implantation Window, Bleeding Timing & hCG Test Dates
Estimate your implantation window (ovulation +6 to +12 days, peak 8-10 DPO), likely implantation bleeding timing vs your expected period, and the earl
Incidence Rate Calculator — Person-Time Rate, Cumulative Incidence & Rate Ratio (Free)
Free incidence rate calculator for epidemiology: compute incidence rate from new cases and person-time (per 1,000 / 10,000 / 100,000 person-years), cu
Infant Tylenol Dosage Calculator by Weight (160 mg/5 mL) — Dose, Tracker & Safety Check
Educational infant/children's Tylenol (acetaminophen 160 mg/5 mL) dose estimator: weight-based dose (15 mg/kg), label chart, 24-hour dose log with nex
IVF Due Date Calculator — EDD by Transfer, Retrieval & FET Date
Free IVF due date calculator: estimate your due date from embryo transfer date (day 3 / day 5 / day 6), egg retrieval date, or frozen embryo transfer (FET) date. Get gestational age, trimester, milestones and equivalent LMP. 100% client-side, no signup.
IVIG Dose Calculator — Total Dose, Infusion Volume & Titration Schedule
Free IVIG dose calculator: estimate total immunoglobulin dose (g), daily dose, infusion volume for 5% or 10% products, and a titrated infusion schedule by weight (kg/lb). Educational estimate only — not medical advice.
Jet Lag Calculator — Recovery Days & Day-by-Day Adaptation Plan
Free jet lag calculator: enter two cities and your flight to get the time difference, jet lag severity, recovery days estimate, a day-by-day adaptation plan (light, sleep, melatonin timing) and an in-flight sleep optimizer. 100% client-side, no signup.
Karvonen Formula Calculator — Target Heart Rate by Heart Rate Reserve
Free Karvonen formula calculator: target heart rate = ((HRmax − HRrest) × intensity%) + HRrest. Choose 220−age, Tanaka (208−0.7×age), or measured max HR. Full 5-zone table, worked steps, and FAQ. 100% client-side.
Kaya Identity Calculator — Decompose CO2 Emissions into 4 Drivers
Free Kaya identity calculator: decompose CO2 emissions into population, GDP per capita, energy intensity and carbon intensity. Solve for a missing factor or compare two scenarios. 100% client-side.
Kidney Failure Risk Calculator (KFRE) — 2-Year & 5-Year CKD Risk Estimate
Free Kidney Failure Risk Equation (KFRE) calculator by Tangri et al. Estimate 2-year and 5-year kidney failure risk from age, sex, eGFR and urine albumin-to-creatinine ratio (ACR). Educational estimate only — not medical advice.
Light's Criteria Calculator — Exudate vs Transudate Pleural Effusion | nrtechstudio.com
Light's criteria calculator: enter pleural fluid and serum protein + LDH to classify a pleural effusion as exudate or transudate. Unit converter, diff
Lille Score Calculator — Steroid Response in Alcoholic Hepatitis (Day 4 / Day 7)
Free online Lille score calculator (Louvet 2007): predicts corticosteroid response in severe alcoholic hepatitis from age, albumin, bilirubin day 0 vs day 4/7, renal insufficiency, and PT. Auto unit conversion mg/dL↔µmol/L, g/dL↔g/L. Educational estimate only — not medical advice.
Local Anesthetic Max Dose Calculator — Weight-Based mg & mL (7 Agents)
Free local anesthetic maximum dose calculator: weight-based limits (mg/kg) for lidocaine, bupivacaine, ropivacaine, mepivacaine, prilocaine, articaine and chloroprocaine, with or without epinephrine. Get max mg, max mL, and dental cartridges. Educational estimate only.
Log Reduction Calculator — CFU, % Kill, D-Value & Dilution
Free log reduction calculator: convert CFU counts to log reduction and percent kill, log↔percent table (1–8 log), D-value contact time, and serial-dilution cumulative log reduction.
Pediatric Maintenance Fluids Calculator — Holliday-Segar & 4-2-1 Rule
Free pediatric maintenance fluids calculator: Holliday-Segar 100-50-20 daily volume and 4-2-1 hourly rate from weight (kg/lb), tiered breakdown, quick reference table, and FAQs. Educational — not medical advice.
Max Heart Rate Calculator — 4 Formulas + Training Zones | nrtechstudio
Estimate your max heart rate with 4 research formulas (Fox, Tanaka, Gulati, Gellish), see all 5 training zones in bpm, and find your fat-burning zone. Free, private, no sign-up.
MCG to IU Converter — Vitamin D, A & E (mcg ↔ IU, mg ↔ IU)
Free mcg to IU converter for vitamin D (1 mcg = 40 IU), vitamin A retinol (1 mcg = 3.33 IU) and vitamin E natural (1.49 IU/mg) / synthetic (2.22 IU/mg). Converts both directions with NIH-verified factors.
Meal Calorie Calculator — Calories & Macros Per Meal
Free meal calorie calculator: build your meal from 60+ common foods with USDA-based calories, get total calories plus protein, carbs and fat breakdown. 100% private, no signup.
Medicine 3 Times a Day Calculator — Schedule & What It Means
Free medicine schedule calculator: what 1, 2, 3, 4 or 6 times a day means (every 24/12/8/6/4 hours), a dose interval planner, and general missed-dose
MELD Score Calculator — MELD & MELD-Na with 3-Month Mortality Estimate
Free MELD calculator: compute MELD and MELD-Na scores from bilirubin, INR, creatinine and sodium (Kamath et al. formula + UNOS/OPTN rules). Unit conversion, dialysis toggle, clamp/cap handling, worked breakdown and published 3-month mortality bands. Educational estimate only — not medical advice.
Mentzer Index Calculator — MCV/RBC Ratio for Thalassemia vs Iron Deficiency | nrtechstudio
Free Mentzer index calculator: MCV divided by RBC count with cutoff 13 (Mentzer, Lancet 1973) plus RDW and RBC-count supporting features to suggest th
MEWS Score Calculator — Modified Early Warning Score (Subbe 2001)
Free MEWS calculator: Modified Early Warning Score from 5 vital signs (Subbe et al., QJM 2001). Risk bands, escalation guidance, and a serial trend tr
Miles to Steps Calculator — Convert Miles, Km and Steps (Height-Based Estimate)
Free miles to steps calculator and converter. Enter miles or km (plus optional height) to estimate steps, or convert steps back to miles and km. Walking stride model, no sign-up.
mmol/L to mg/dL Converter — Glucose, BUN & Creatinine
Free mmol/L to mg/dL converter for blood sugar (glucose ×18.0182), BUN/urea (×0.357) and creatinine (×88.4 µmol/L). Two-way conversion with transparent factors, molecular weights, reference ranges and worked examples.
Mortality Rate Calculator — Crude, Cause-Specific, Case-Fatality, IMR (Free)
Free mortality rate calculator for epidemiology: crude mortality rate, cause-specific mortality rate, case-fatality rate (CFR), infant mortality rate
Mulch Calculator | Cubic Yards, Bags & Cost | nrtechstudio
Free mulch calculator: bed area × depth to cubic yards, bags of mulch, bulk vs bag cost comparison, and annual re-mulch top-up. Works in feet/meters, inches/cm.
Mutation Frequency Calculator
Free mutation frequency calculator: f = mutants / total screened, Wilson score confidence interval, frequency ↔ mutation-rate conversion, and the Luria-Delbrück fluctuation test (p0 method). Populatio
Mutation Rate Calculator — Per-Base Rate, Mutations per Genome & Reference Table
Free mutation rate calculator: estimate mu from de novo mutation counts (mu = M / (N x G)), convert mutations per base pair per generation to per-genome and per-year rates, and compare verified rates
Navy PRT Calculator — US Navy Physical Readiness Test Score (2025 Standards)
Free Navy PRT calculator using the official Guide-5A (Dec 2025) scoring tables. Score push-ups, forearm plank, 1.5-mile run, 2km row, or swim by age and gender — plus overall PRT score and pass/fail.
NEDOCS Score Calculator — National Emergency Department Overcrowding Scale
Free NEDOCS calculator: compute the National Emergency Department Overcrowding Scale score (Weiss et al. 2004) from 7 operational inputs, see the 6 se
Ovulation Calculator — Fertile Window & Ovulation Day Estimator
Free ovulation calculator: enter your last period date and cycle length to estimate ovulation day, your 6-day fertile window, and your next 3 periods. Transparent calendar-method formula, 3-month calendar, no signup.
Oxygenation Index Calculator — OI Formula & ECMO Thresholds | nrtechstudio
Free oxygenation index (OI) calculator: OI = (FiO2 x MAP x 100) / PaO2 with FiO2 fraction/percent toggle, PaO2 mmHg/kPa, OSI alternative, target-OI in
Pack Years Calculator — Smoking History in Pack-Years
Free pack years calculator: convert cigarettes per day and years smoked into pack-years, with multiple smoking periods, lifetime cigarette totals, exposure bands, and educational lung-cancer screening context. 100% client-side, no signup.
Padua Score Calculator — VTE Risk in Hospitalized Medical Patients | nrtechstudio
Free Padua Prediction Score calculator: 11 weighted risk factors for venous thromboembolism in hospitalized medical patients, live score 0-20, low/hig
Parkland Formula Calculator — 24-Hour Burn Fluid Resuscitation
Parkland formula (Baxter) calculator: calculate fluid needs for the first 24 hours of burn resuscitation — 4 mL × kg × %TBSA, 8-hour / 16-hour split, mL/hour rate, urine output target, child mode + rule of nines & Lund-Browder helper. Educational, not medical advice.
Peak Flow Calculator — Predicted PEF, Asthma Zones & Diurnal Variability
Free peak flow calculator: predicted PEF from age, sex and height (Nunn & Gregg 1989), asthma action-plan zones from your personal best, diurnal varia
Pearl Index Calculator — Measure Contraceptive Effectiveness
Free Pearl Index calculator: enter pregnancies and exposure to compute the Pearl Index (pregnancies per 100 woman-years). Includes perfect-use vs typi
PECARN Calculator — Pediatric Head Injury CT Decision Rule (Kuppermann 2009) | nrtechstudio
Free PECARN pediatric head injury calculator (Kuppermann et al., Lancet 2009): age-specific predictors for children under 2 and ages 2–17, ciTBI risk
Pediatric Blood Pressure Percentile Calculator (AAP 2017) — nrtechstudio
Free pediatric blood pressure percentile calculator using the AAP 2017 normative tables (Flynn et al.). Enter age, sex, height, systolic & diastolic BP to get estimated BP percentiles and the AAP 2017 category: normal, elevated, stage 1 or stage 2. Educational use only.
Pediatric Epworth Sleepiness Scale (ESS-CHAD) Calculator — Child Daytime Sleepiness Test
Free ESS-CHAD calculator: the Epworth Sleepiness Scale for Children and Adolescents (Janssen et al.). Answer 8 questions, get the 0-24 score with norm
Peptide Reconstitution & Dosage Calculator — mg to mL to U-100/U-40 Syringe Units
Educational math only: convert peptide vial mg + water mL into concentration (mg/mL), draw volume (mL), and U-100 or U-40 insulin-syringe units; solve for diluent volume at a target concentration. Makes no dose recommendations.
Percentage Calculator — What Is X% of Y, X Is What % of Y, % Change — nrtechstudio
Free 3-in-1 percentage calculator: what is X% of Y, X is what percent of Y, and percent change old → new. Show-your-work steps, exact fractions, honest rounding notes. 100% client-side — your numbers never leave your browser.
PHEV Economy Calculator — Blended MPGe, Cost per Mile & Payback
Free plug-in hybrid economy calculator: blended MPGe from your electric miles (kWh) and gasoline gallons, monthly energy cost, cost per mile split, savings vs a gas-only car, and payback on the PHEV p
Pine Straw Calculator — How Many Bales Do I Need?
Free pine straw calculator: how many bales you need for your beds, bale to square-foot coverage converter, pine straw vs mulch cost per sq ft, and annual re-mulch top-up. Coverage rates verified from
Plastic Footprint Calculator — Estimate Your Annual Plastic Use
Free plastic footprint calculator: enter your weekly and monthly plastic habits to estimate kilograms of plastic per year, see bottle equivalents, and get reduction tips ranked by impact.
Prostate Volume Calculator — Ellipsoid (TRUS/MRI)
Free prostate volume calculator using the ellipsoid formula (length × width × height × π/6 or ×0.52) from ultrasound or MRI dimensions. Includes PSA density, size interpretation, and worked example. Educational use only — not medical advice.
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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.