Free Online Tools for Everything You Do
Browse 2,706+ free interactive tools - home improvement estimators, pet calculators, cooking converters, automotive tools, finance planners, fitness calculators, developer utilities and more. No sign-up. 100% private. Runs entirely in your browser.
Greenhouse Size Calculator — Plants, Ventilation, Heater BTU & Water
Free greenhouse size calculator: plan floor space, bench layout, ventilation CFM, heater BTU, glazing area and daily water needs for any hobby greenho
CSS Grid Calculator — Column Widths & Layout Generator
Calculate CSS grid column widths in seconds — fixed & fluid 12-column layouts, gutter math, breakpoint presets & copy-ready CSS/Tailwind code. 100% client-side.
CSS Grid Generator
Free visual CSS Grid layout builder — design grid-template-areas, responsive auto-fit tracks and breakpoints, export clean CSS + HTML.
Gross Margin Calculator — Free
Free gross margin calculator: Rp & percent margin, markup conversion, 3-way target margin solver, A vs B comparator, COGS scenario table. 100% in-browser.
Gross Pay Calculator — Hourly, Salary, Overtime, Bonus, Commission & Tips
Free gross pay calculator: compute gross wages from hourly rate × hours, overtime at 1.5× (FLSA), double time, salary, bonuses, commissions and tips — shown weekly, biweekly, monthly and annually.
Property GRM (Gross Rent Multiplier) Calculator — Free
Free property GRM calculator: compute gross rent multiplier from price and rent, implied price/rent solver, compare 2 properties, GRM vs rental yield.
Ground Speed Calculator - Wind Triangle, WCA & Flight Time
Free ground speed calculator for pilots. Enter true airspeed and the wind vector to solve the wind triangle: wind-corrected ground speed, wind correction angle, headwind/tailwind/crosswind components,
Grow Light Lab — PPFD, DLI & Hanging Distance Calculator
Free grow light photometry suite: hanging distance calculator (inverse-square law), lux/lumen/foot-candle to PPFD spectrum converter, PPFD↔DLI solver, LED wattage & coverage sizer, and growth-stage PPFD/DLI targets. 100% client-side.
Growing Annuity Calculator — PV, FV & Solver
Free growing annuity calculator: present value & future value of payments growing g% per period, PMT1/g/r/n solver, growing vs level annuity comparison.
India GST Calculator — Calculate CGST, SGST & IGST (Add, Remove, Compare)
India GST calculator: add GST to base price, remove GST from inclusive price, compare two rates, find effective rate. CGST/SGST/IGST split. Free.
GST QST Calculator Quebec — 5% GST + 9.975% QST (2026)
Free GST QST calculator for Quebec: add or remove 5% GST + 9.975% QST from any price. Exact breakdown, reverse tax calculator, and Canada province comparison.
GTIN Check Digit Calculator (GS1 Modulo 10) — Free, No Signup
Free GS1 GTIN check digit calculator. Compute the modulo-10 check digit for GTIN-8, GTIN-12 (UPC-A), GTIN-13 (EAN-13) and GTIN-14, validate complete GTINs, or batch-process many numbers. 100% client-side.
Guest Room Size Calculator — 7 Layout Modes for the Perfect Guest Bedroom
Free guest room size calculator: 7 layout modes for bed fit, walkway clearance, dresser, luggage zone, ensuite vs shared bath, closet and room planner
Guinea Pig Age Calculator — Guinea Pig Years to Human Years
Free guinea pig age calculator: convert guinea pig years to human-year equivalents with month-level precision. Milestone-based ranges (1 yr ≈ 20–25), life stages, age chart. 100% client-side, estimate
Guinea Pig Cage Size Calculator — Cage Size, C&C Grids & Bedding
Free guinea pig cage size calculator: ideal floor area for 1-6 guinea pigs (HSUS minimums + recommended tiers), check-your-cage verdict, ft²↔m² converter, C&C grid planner, and bedding volume calculat
Guinea Pig Pregnancy Calculator — Due Date, Week-by-Week Timeline & Care
Free guinea pig pregnancy calculator: estimate due dates from breeding date (59–72 days, avg 68), week-by-week pregnancy stages, litter size guide, and pre/post-natal care checklists. Estimates only —
Guitar Scale Finder — Reverse Scale Lookup from Notes, Chords Fretboard
Free online guitar scale finder with reverse lookup: enter notes or tap frets to identify the scale, find scales from chord progressions, browse 48 scales with interactive fretboard diagrams and audio playback. 6 & 7 string.
Guitar String Tension Calculator — Per-String & Full Set (lb / kg / N)
Calculate guitar string tension in lb, kg or N. Single-string calculator with gauge picker, scale length and tuning, plus a full 6-string set table with total tension and balance bars. Based on published D'Addario unit weights.
GWh to kWh Conversion – Energy Unit Converter
Free GWh to kWh conversion, joules to units, megawatt to kWh conversion, and convert kWh to GWh calculator.
Hair Diffraction Calculator — Measure Hair Diameter with a Laser
Measure hair diameter from laser diffraction (a·sin θ = mλ). Diameter & fringe-prediction modes, error estimation, experiment diagram, procedure guide.
Hall Coefficient Calculator (R_H) — Hall Effect, Hall Voltage
Hall coefficient calculator: R_H = 1/(n·q) from carrier concentration, carrier type from R_H sign, Hall voltage V_H = R_H·I·B/d. Cu/Ag/Si/Ge presets.
Hammock Stand Size Calculator — Stand Length, Weight Capacity & Hang Angle (Free)
Free hammock stand size calculator: stand length, weight capacity, 30-degree hang angle, footprint planner and cost estimator. Private, in your browser.
Hamster Age Calculator — Hamster Years to Human Years
Free hamster age calculator: convert hamster age to human-year equivalents with month-level precision (1 yr ≈ 58), reverse conversion, species lifespans, life stages, birthday milestone calendar. 100%
Hangboard Trainer Timer — Free Online Hangboard Timer (Repeaters, Max Hangs)
Free online hangboard timer with sound: repeaters 7/3, max hangs, min-edge, density hangs protocols, custom session planner and progress log. No app install, no sign-up — runs 100% in your browser.
Hardness Conversion Calculator: Brinell, Vickers, Knoop, Shore and Mohs
Convert hardness between Brinell (HB), Vickers (HV), Knoop (HK), Shore A/D, and Mohs with an approximate conversion calculator, Brinell/Vickers/Knoop test calculators, a chart, and inline reference tables. Free, client-side.
Harmonic Wave Equation Calculator y = A·sin(kx ± ωt + φ) — nrtechstudio.com
Harmonic wave equation calculator: compute displacement y(x,t) = A·sin(kx ± ωt + φ), break the equation into A, k, ω, φ, propagation direction, λ, f, T, v = ω/k, plus an animated wave visualization.
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.
MD5 Hash Generator & Checksum Verifier
Interactive online MD5 hash generator, cryptographic checksum verifier, file integrity maker, and HMAC-MD5 tool.
SHA256 Hash Generator & Crypto Calculator
Standalone professional SHA256 hash generator, cryptographic calculator, and secure hash algorithm generator. Hash string sha256, sha-384, sha-512 with HMAC support and live verification.
Hash Identifier Online — Identify MD5, SHA256, bcrypt & 300+ Hash Types (Free)
Free online hash identifier. Paste any hash to instantly identify MD5, SHA1, SHA256, SHA512, bcrypt, NTLM, WordPress, Django & 300+ hash types. 100% client-side — your hashes never leave your browser. No signup.
Hashtag Generator — Free Instagram, TikTok YouTube Hashtag Tool (No Sign-Up)
Free hashtag generator with 60+ curated niches, banned-hashtag filter, and per-platform optimizer for Instagram (30 max), TikTok (3-5), YouTube, X, LinkedIn & more. No sign-up, no AI gimmicks — 100% private, runs in your browser.
Hat Size Calculator — Cast-On, Crown Decrease & Brim Planner for Knit Hats
Free hat size calculator for knitters: cast-on stitches from head size and gauge with negative ease, baby-to-adult size chart, round-by-round crown decrease planner, brim/ribbing calculator, and slouchy vs fitted modes. 100% private, works offline.
Egg Incubation Calculator — Hatch Date, Temperature & Humidity Chart, Candling & Brooder Planner
Free egg incubation calculator & hatching suite: hatch-date calculator with day-by-day milestones for chicken (21d), duck (28d), quail (18d), goose (30d); incubator temperature & humidity planner (dry vs wet hatch, still-air vs forced-air); candling schedule; lockdown countdown; hatch-rate estimator; brooder temperature & space planner. 100% client-side.
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.
Headline Analyzer — Score Your Headlines for Impact
Free headline analyzer: score any headline 0-100 for impact. Checks word balance (common, uncommon, emotional, power words), ideal length, sentiment and structure, with Google SERP, email and social previews. 100% client-side.
Headphone Power Calculator — mW, Vrms & Source Checker
How much power do your headphones need? Enter sensitivity and impedance to get required mW, Vrms, V peak and mA for any target SPL, convert dB/mW to dB/V, and check if your dongle, laptop or amp can drive them.
Health Insurance Plan Comparison Lab — HDHP vs PPO, HSA & Monte Carlo Simulator (2026)
Free health insurance plan comparison calculator: compare two plans side by side, run a Monte Carlo cost simulator, find the break-even spending level, estimate HSA tax savings (2026 IRS limits), and check family vs individual coverage. Educational estimates, 100% client-side.
Heart BPM Calculator & Pulse Rate Counter
Interactive heart BPM calculator, live tap tempo pulse counter, target training zones, and beats per minute analyzer.
Heart Rate Zone Calculator — Karvonen, LTHR, Friel, Maffetone (5 Methods)
Free heart rate zone calculator with 5 methods side by side: % of max HR, Karvonen (HRR), LTHR, Joe Friel 7-zone, and Maffetone 180 formula. 3 max-HR estimators (Fox, Tanaka, Nes), running / cycling / swimming presets, method-agreement analysis, and watch-ready zone copy for Garmin, Apple Watch, Coros and Zwift. 100% client-side.
Heat Index Calculator — Apparent Temperature (Rothfusz NWS Formula)
Compute the heat index (apparent temperature) from temperature and relative humidity with the official NWS/NOAA Rothfusz formula. °F/°C input, result + danger categories and safety advice.
Heat Loss Calculator — Room-by-Room BTU/hr Heat Loss | nrtechstudio.com
Room-by-room heat loss calculator: BTU/hr envelope loss with U-value material database, ventilation ACH, thermal bridging, heater sizing and energy co
Heat Transfer Coefficient Calculator — U-Value, R-Value & Unit Converter | nrtechstudio.com
Free heat transfer coefficient calculator: convert W/m²·K to BTU/(hr·ft²·°F) and kcal/(h·m²·°C), compute multi-layer wall U-value & R-value per ISO 6946, and heat loss Q = U·A·ΔT. 100% in-browser, no sign-up.
Hedge Ratio Calculator: Number of Futures Contracts for Hedging
Compute the hedge ratio: number of futures contracts to hedge a spot exposure, optimal hedge ratio h* = ρ × (σ_S/σ_F), and hedge effectiveness. Free, 100% in the browser.
Height & Weight Calculator
High-precision Child Adult Height Predictor, Ideal Body Weight Calculator, and Anthropometric Analysis Suite.
Height Converter: Feet and Inches to CM (5'10" Style Input)
Convert height between feet+inches and centimeters, both ways. Type 5'10" directly, see a full conversion chart, BMI healthy weight range, and worked examples.
Heisenberg Uncertainty Principle Calculator (Δx·Δp ≥ ħ/2)
Compute the Heisenberg uncertainty limit: two-way Δx ↔ Δp solver, energy–time mode ΔE·Δt ≥ ħ/2, electron, proton, and macroscopic dust examples, plus ħ vs h explained.
Helical Coil Calculator — Wire Length, Air-Core Inductance (Wheeler) & Turns Solver
Free helical coil calculator: coil winding wire length, single-layer air-core inductance (Wheeler 1928), reverse turns solver for a target inductance, LC resonant frequency, AWG magnet-wire table. Metric & imperial. 100% client-side.
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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.