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.
Gear Diametral Pitch Calculator (P = N/D) + Metric Module Conversion
Free diametral pitch calculator: compute P from tooth count & pitch diameter (P=N/D), convert diametral pitch to metric module (m=25.4/P), circular pitch, addendum, dedendum & whole depth. 100% client-side.
Diamond Weight Calculator — Carat to Grams, Points & mm Size Estimate
Free diamond weight calculator: convert carats to grams, milligrams and points (1 ct = 200 mg exact), and estimate carat weight from millimeter diameter by cut shape. 100% client-side.
Diaper Cost Calculator — Diapers Per Day by Age, Cloth vs Disposable Break-Even
Free diaper cost calculator and usage planner: how many diapers per day by age, total diapers to potty training, cloth vs disposable cost comparator with break-even months, store vs premium vs eco diaper tiers, and multi-child savings. 100% client-side, no signup.
Dice Roller Online — Roll Dice with Exact Probability Calculator
Free online dice roller with exact probability calculator: roll 3d6, 2d20kh1, 4d6dl1, d100 & more. D&D 5e advantage/disadvantage, distribution charts, dice statistics & chi-square fairness test. No ads, no signup, 100% client-side.
Text Comparison & Diff Checker
Professional online text comparison tool to compare two texts for differences, find difference between two texts, and check similarity with highlighted diff output.
Difference of Two Squares Calculator — Factor a²−b² with Steps
Factor any difference of two squares — x²−9, 4x²−25, x⁴−16 — into (a−b)(a+b) with full step-by-step working, GCF extraction, expand-back verification, and honest handling of sums of squares.
Digits to Words Converter: Spell Numbers in English
Free digits to words converter. Convert digits to words in English: 1234 becomes one thousand two hundred thirty-four. Indian numbering (lakh, crore), USD/INR/IDR currency, check-writing style, decimals and ordinals. 100% client-side.
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
Dilution Ratio Calculator — Mix Ratios, C1V1, ppm & Cost | nrtechstudio.com
Dilution ratio calculator: mix 1:10, 1:99 and label ratios (bleach, Roundup, Simple Green), C1V1 solver, ratio-to-ppm converter, cost per gallon.
Dimensional Weight Calculator: DIM Weight & Billable Weight (UPS, FedEx, DHL)
Free dimensional weight calculator: DIM weight = (L x W x H) / divisor. Compare UPS/FedEx (139) vs DHL (166) and find your billable shipping weight instantly.
Dining Table Size Calculator — Rectangular, Round, Square & Oval | nrtechstudio.com
Free dining table size calculator: what size table seats 4, 6 or 8? Rectangular, round, square & oval sizers, room fit and clearance — inches or cm.
Dipole Moment Calculator
Electric dipole moment calculator: p = q × d in C·m and debye, q & d inverses, and potential energy U = −pE cos θ and torque τ = pE sin θ in an electric field. H₂O, HCl, NH₃, CO presets.
Direct Material Price Variance (MPV) & Quantity Variance Calculator — nrtechstudio
Calculator for direct material price variance (MPV), material quantity variance (MQV), and total direct material variance with automatic favorable/unfavorable classification.
Master Website Directory & Sitemap Hub
Clean, structured directory of all developer utilities and technical articles without AI slop.
Discretionary Income Calculator — Dept of Education & BEA Definitions (2026)
Free discretionary income calculator: Department of Education definition (AGI minus 150% of the 2026 HHS poverty guideline), BEA budgeting definition, IDR student-loan payment what-if, and the full 2026 poverty guideline table. 100% client-side.
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.
Displacement Calculator — s = v·t, Constant Acceleration & Solver
Free 1D kinematics displacement calculator: s = v·t (constant velocity), s = v0·t + ½·a·t² (constant acceleration), s = (v² − v0²)/(2a), and missing-variable solver. Supports m, km, cm, mm, miles, feet.
Disposable Income Calculator — Gross to Disposable, Allocation & Savings Rate
Calculate disposable income (gross − taxes − mandatory contributions), 50/30/20 allocation, savings rate, and compare salary-raise scenarios. Free, 100% in your browser.
Distance Attenuation Calculator — Sound Level Drop Over Distance | nrtechstudio.com
Free distance attenuation calculator: enter the SPL at a reference distance and get the sound level at any target distance using L2 = L1 − 20·log10(d2/d1) for point sources (or 10·log10 for line sources). Includes reverse mode, distance–SPL table, and 16 FAQs. 100% in-browser, no sign-up.
Distance to Horizon Calculator – nrtechstudio.com
Calculate the distance to the horizon from eye height, height from an observed horizon distance, and the line-of-sight distance between two elevated points (lighthouse). With atmospheric refraction option. Free, 100% client-side.
Distance Between Two Points Calculator (2D, 3D & Minecraft) | NR Tech Studio
Free distance between two points calculator: Euclidean, Manhattan and Chebyshev distance in 2D and 3D, step-by-step formula, visualization, plus Minecraft block distance and Nether to Overworld coordinate converter (x8 / divide by 8).
Dive Weight Lab — Scuba Weight Calculator & Buoyancy Suite (Free)
Free scuba weight calculator: how much dive weight you need from body weight, wetsuit thickness, salt vs fresh water, tank type and experience. Plus tank-swing explainer, salt/fresh converter, weight-check protocol, distribution planner and wetsuit buoyancy table. 100% client-side, no signup.
Dividend Discount Model (DDM) Calculator — Gordon Growth Model
Estimate a stock's fair value with the Dividend Discount Model: single-stage Gordon Growth, two-stage (multi-stage) DDM, implied-growth solver from market price, and an r × g sensitivity table.
Dividend Payout Ratio Calculator — Formula, Solver & Comparator
Calculate dividend payout ratio (total dividends ÷ net income × 100%), reverse earnings/dividend solver, retention ratio & sustainable growth rate, and compare two companies. Free.
Stock Dividend Calculator — Total Dividends, Projections & DRIP
Calculate stock dividend amounts: total dividends from DPS × share count, target-dividend solver, dividend growth projections, and DRIP simulation. Free, 100% in your browser.
Divorce Cost Calculator — Uncontested vs Mediation vs Contested (2026) | nrtechstudio.com
Free divorce cost calculator: compare uncontested, mediation & contested divorce costs with per-state filing fees (50 states), complexity adjuster, timelines, hidden costs & mediation vs litigation break-even. Educational estimates — not legal advice.
DMS to Decimal Degrees Converter
Free DMS to decimal degrees converter. Convert degrees minutes seconds to decimal degrees, decimal degree to DMS, coordinate degrees minutes and seconds to decimal coordinates.
DMS to Decimal – Degrees Minutes Seconds Coordinate Converter
DMS to decimal, latitude decimal conversion, convert longitude to decimal degrees, lat lon to decimal degrees, degree minutes to decimal degrees, latitude coordinates converter, convert GPS to decimal, degrees min sec to decimal degrees, and more.
DNA Concentration Calculator — A260 to ng/µL, Purity & Yield | nrtechstudio.com
Free DNA concentration calculator: convert A260 absorbance to ng/µL for dsDNA, ssDNA, RNA and oligos, with dilution factor, pathlength correction (NanoDrop), A260/A280 & A260/A230 purity ratios, and total yield. 100% client-side — your data never leaves the browser.
DNA Copy Number Calculator — ng/µL to Copies, Plasmid & qPCR Dilution Planner
Free DNA copy number calculator: convert ng/µL to copies/µL with Avogadro
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
D&D 5e Money Converter — Convert cp, sp, ep, gp, pp & Split Loot
Free D&D 5e currency converter: convert copper (cp), silver (sp), electrum (ep), gold (gp) and platinum (pp) pieces in any mix, and split treasure evenly between party members. 100% client-side.
DNS Lookup Tool & DNS Toolbox
High-performance DNS lookup tool, DNS search tool, zone file generator, nameserver finder, and CLI command generator.
DNS WebRTC Leak Test — Check for IP, DNS IPv6 Leaks (Free)
Free DNS & WebRTC leak test. Find out if WebRTC exposes your real IP address, detect IPv6 leaks, and learn exactly what a DNS leak test can and cannot check. Runs in your browser — no signup.
DNS Zone File Generator
Interactive RFC 1035 BIND DNS zone file generator, DNS record generator tool, and creating DNS configuration online.
Dog Age Calculator: Dog Years to Human Years
Free dog age calculator: convert dog years to human years with 4 size profiles and 3 methods side-by-side — AVMA, AKC chart, Wang 2020. 100% client-si
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 Calorie Calculator — Daily kcal by Weight, Age & Activity | nrtechstudio.com
Free dog calorie calculator: estimate daily kcal needs with the veterinary RER formula (70×W^0.75) × life-stage factors. Includes meal planner, 10% treat budget, kcal→grams/cups food converter and a weight-loss planner.
Dog Chocolate Toxicity Calculator — Theobromine Dose & Risk Zones | nrtechstudio.com
Free dog chocolate toxicity calculator: enter your dog
Dog Crate Size Calculator — Dog Crate Size Chart
Free dog crate size calculator: enter your dog's length & height (or pick a breed) to get recommended crate dimensions, size category, measuring guide, and breed table.
Dog Harness Size Calculator — Find the Right Harness Size (XXS–XL)
Free dog harness size calculator: enter neck girth + chest girth to get the right harness size (XXS–XL), with measuring guide, fit rules, and harness-type advice.
Dog Heat Cycle Calculator — Predict Next Heat & Fertile Window
Free dog heat cycle calculator: enter your dog's last heat start date and average cycle length to estimate the next 3 heat cycles, the fertile window, peak fertility days, and the 4 phases (proestrus,
Dog House Size Calculator — Dimensions, Door, Insulation & Cost
Free dog house size calculator: interior dimensions by breed or measurements, door opening, insulation plan, material list and build cost. 100% client-side.
Dog Life Expectancy Calculator — How Long Do Dogs Live? (Breed + Size)
Free dog life expectancy calculator: pick breed or size class + current age to get a lifespan range, years remaining, and epigenetic human-age equivalent (Wang 2020). Population averages, not a predic
Metacam Dosage Calculator for Dogs — Meloxicam mg + mL by Weight (Day 1 vs Maintenance)
Estimate Metacam (meloxicam) dose for dogs by weight per the FDA label: 0.2 mg/kg on day 1, then 0.1 mg/kg daily — converted to mL of 1.5 mg/mL suspension, syringe marks, and drops. Educational estima
Dog Onion Toxicity Calculator — How Much Onion Is Toxic to Dogs
Free dog onion toxicity calculator: enter your dog's weight and the onion or garlic type and amount to estimate the dose in g/kg and risk zone, based on veterinary literature. Estimate only — call you
Dog Pregnancy Calculator — Due Date & Whelping Timeline
Free dog pregnancy calculator: enter the breeding or ovulation date and get an accurate due-date window, week-by-week canine gestation timeline, whelping checklist, and calendar reminders. 100% client-side, no signup.
Dog Quality of Life Calculator — HHHHHMM Scale (2026) | nrtechstudio.com
Free dog quality of life calculator based on the HHHHHMM scale (Hurt, Hunger, Hydration, Hygiene, Happiness, Mobility, More good days than bad). Score 7 factors, track trends over time, and print a summary for your vet. Private, no signup.
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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.