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.
dB Gain Calculator — Voltage, Power & dBm Converter | nrtechstudio.com
Free dB gain calculator: convert voltage gain to dB (20 log10), power gain to dB (10 log10), dB back to voltage and power ratios, dBm/dBW to watts, and add up cascade gains. 100% in-browser, no sign-up.
dBm to mW Converter: RF Power Conversion Calculator
Free dBm to mW calculator. Convert dBm to milliwatts, watts and dBW instantly with the formula P(mW) = 10^(dBm/10). Includes dBm to watts conversion table and WiFi signal strength guide.
dBm to Watts Converter: dBm, W, mW, dBW
Free dBm to watts calculator. Convert dBm to watts, milliwatts and dBW two ways, with the conversion formula, a dBm to watts table, and reference power levels.
DC Wire Size Calculator — Solar, RV & Automotive (AWG by Amps, Length & Voltage Drop) | nrtechstudio.com
Free DC wire size calculator for solar, RV and automotive wiring. Enter amps, system voltage (12/24/48V DC or any voltage), one-way length and max voltage drop to get the smallest copper or aluminum AWG that passes ampacity and drop limits. Includes voltage-drop formula, ampacity chart, fuse sizing and 16 FAQs. 100% client-side, no signup.
de Broglie Wavelength Calculator λ = h/p
de Broglie wavelength (matter wave) calculator: compute λ = h/p from mass & velocity, from kinetic energy, relativistic version, and inverse mode from measured λ. Electron, proton, neutron presets. SI 2019 constants + CODATA 2018. Free, 100% client-side.
Deadlift Max Calculator — Estimate Your 1RM (Epley, Brzycki, Lombardi)
Free deadlift max calculator: estimate your deadlift 1RM from weight × reps with Epley, Brzycki and Lombardi formulas. Training % table, rep-max reverse, plate loader, kg/lb.
Deadweight Loss Calculator
Interactive deadweight loss calculator: tax DWL, elasticity-based DWL, subsidy DWL, price ceiling/floor, Harberger triangle visualization, and consumer vs producer tax burden analysis.
Debt Consolidation Calculator — Compare Debts vs Consolidation Offer
Compare your current debts' total payments and interest against a consolidation loan offer: monthly payment (PMT), total interest, fees, monthly savings, and fee break-even point. 100% in your browser.
Debt Payoff Calculator — Snowball vs Avalanche Planner | nrtechstudio.com
Free debt payoff calculator: compare snowball vs avalanche strategies across up to 10 debts, see your debt-free date, total interest, month-by-month timeline, and what-if scenarios. 100% private — runs in your browser.
Debt to Equity Ratio Calculator — D/E, Conversion Simulator & Industry Benchmarks
Free debt to equity ratio calculator: compute D/E, debt to assets, and equity multiplier, check verdict bands by industry, and simulate debt-to-equity conversion with dilution impact. 100% private — runs in your browser.
Debt to Income Ratio (DTI) Calculator — Front-End & Back-End
Calculate front-end and back-end debt-to-income (DTI) ratios from monthly payments and gross income. 36%/43%/50% verdict bands, payoff what-if simulation, general 28/36 rule for mortgages, plus mortgage mode: P&I estimator, PITI, 43% QM check, and 28/36 & 31/43 affordability limits.
Decimal to ASCII & Text Converter Online
Free online decimal to ASCII converter, decimal to text translator, and character to ASCII converter. Convert decimal to ASCII code and ASCII to decimal table.
Decimal to Base & Number Base Converter Online
Free online number base converter, base to base converter, and decimal converter. Convert decimal to base 2, number base calculator, and decimal to floating point converter.
Dec To Bin
Convert decimal (base 10) numbers to binary.
Hex & RGB Color Converter with Pantone Matcher
High-precision decimal, RGB to hex converter, hex code to color name finder, and hexadecimal to Pantone color converter.
Dec To Hex
Convert decimal (base 10) to hexadecimal.
Decimal to IP — Convert Decimal Number to IPv4 Address
Convert any decimal number to its IPv4 address with the full step-by-step division shown. Free online decimal to IP converter with batch mode, binary/hex views, class/scope detection, validation and worked examples. 100% client-side.
Decagon Area Calculator — Area, Perimeter & Side Length of a Regular Decagon
Free decagon area calculator: compute the area, perimeter, side length, circumradius, inradius (apothem) and diagonals of a regular decagon from any one known measurement.
Decimal Odds Converter & Calculator — Fractional, American, Implied Probability
Free decimal odds converter: convert between decimal (European), fractional (UK), American moneyline and implied probability. Payout, parlay, no-vig fair odds and each-way calculator included.
Decimal to Octal Converter | Free Online Base 8 Conversion Tool
Free decimal to octal converter: convert decimal to octal and octal to decimal instantly, with long-division steps, a 0-64 octal chart, and Unix chmod permission context.
Decimal to Ratio Calculator: Convert Decimals, Percents and Ratios
Free decimal to ratio calculator. Convert any decimal to a ratio in simplest form (0.75 becomes 3:4), turn ratios back into decimals, and convert percents to ratios. Includes a common conversion table, step-by-step working, and real-life uses in odds, aspect ratios, and recipes.
Decimal to Text Converter
Interactive decimal byte sequence to ASCII and UTF-8 plain text string decoder with automatic delimiter detection.
Decision Matrix Calculator — Weighted, Pugh, RICE & Sensitivity Analysis (Free, No Signup)
Free online decision matrix calculator, builder and maker: weighted scoring matrix, Pugh matrix, RICE & ICE prioritization, sensitivity analysis, ready-made templates, CSV export and printable report. 100% client-side, no signup.
Deck Material Calculator — Boards, Joists, Beams, Footings Cost (Free)
Free deck material calculator: full material takeoff — decking boards, joists, beams, posts, footings, screws, railing, balusters, stairs — plus IRC span-table checks, hot-tub load mode, metric/imperial and a cost estimator. 100% private, runs in your browser.
Deck Size Calculator — 7 Ways to Size Your Deck
Deck size calculator: 7 modes — guests, furniture zones, yard fit, standard sizes, dining layout, per-person area, house proportion. Free, client-side
Deck Stain Calculator
Free deck stain calculator: coverage, coats, cost and drying time.
Decode the URL & Online Query Parser
Interactive URL decoder, percent-encoding parser, and query string parameter inspector online.
Default Robots.txt Generator & Tester
Interactive robots.txt builder, syntax tester, and SEO crawler rules generator for Googlebot, Bingbot, and search engines.
Defensive Interval Ratio (DIR) Calculator — Measure Defensive Liquidity
Calculate the defensive interval ratio: (current assets − inventory) ÷ daily operating expenses. Includes a target DIR solver, 2-company comparator, interpretation table, and DIR vs current ratio vs cash ratio FAQ.
Deferred Fixed Annuity Calculator — Surrender Charges, MVA & Growth
Free deferred fixed annuity calculator: model guaranteed-rate accumulation, year-by-year surrender charge schedules, 10% free withdrawals, market value adjustment (MVA), and compare vs CDs. Planning estimates only — not financial advice.
Deferred Payment Loan Calculator — Cost of Deferment, Amortization & CSV
Free deferred payment loan calculator: compute the balance after a deferment period (accruing vs non-accruing interest), monthly payment, total interest, cost of deferment, full amortization schedule with CSV download, and compare with vs without deferment.
Split Complementary Colors – Color Harmony & Palette Tool
Split complementary colors, define split complementary colors, split complementary color scheme examples, complementary color tool.
Degree of Operating Leverage (DOL) Calculator — Compute Operating Leverage
Free DOL (degree of operating leverage) calculator: compute operating leverage from volume, price, variable costs, and fixed costs, percent-change version, simulator, plus DOL vs DFL vs DCL comparison.
Degrees to DMS Converter — Decimal to Degrees Minutes Seconds | nrtechstudio.com
Free degrees to DMS converter: decimal degrees to degrees-minutes-seconds and back, with show-your-work steps, N/S/E/W hemisphere, batch mode, and 4 copy formats. 100% private — runs in your browser.
Degrees to Radians Converter - Free Online Tool
Free degrees to radians converter and radians to degrees converter. Instant two-way conversion with the formula rad = deg x pi/180, a common-angles table in terms of pi, and worked examples.
Dehumidifier Size Calculator (Pints/Day) | nrtechstudio.com
Dehumidifier size calculator: the right pints/day for your room from the AHAM chart, basement and ceiling corrections, DOE 2019 ratings, plus running
Delay Time Calculator — BPM to ms, Pre-Delay, Compressor Song Length Studio
Free BPM timing studio: convert BPM to delay time in ms (dotted eighth, triplet, slap), reverb pre-delay & decay, compressor attack/release starters, LFO Hz, song length from bars, speaker distance feet-to-ms, and ms↔Hz. 100% private, runs in your browser.
Delta to Wye (Δ-Y) Conversion Calculator — 3-Phase Balanced & Unbalanced
Free delta to wye conversion calculator: balanced Δ-Y (Z_Y = Z_Δ/3), unbalanced delta to wye and wye to delta transformations, R/L/C networks with frequency, plus 3-phase line vs phase voltage/current and power. 100% client-side — no data leaves your browser.
Density Altitude Lab — Density Altitude Calculator, TAS & Performance Suite
Free density altitude calculator with humidity correction, pressure altitude, ISA atmosphere model, true airspeed/Mach converter, and Koch-chart takeoff & climb performance estimator. Metric & imperial.
Density Converter Online
Free density converter and mass density conversion calculator. Convert kg m3 to lb ft3, kg m 3 to g cm 3, g cm3 to kg m3, density unit converter.
Cylinder Density Calculator — Mass, Volume & Density
Free cylinder density calculator: enter any two of mass, radius+height, or density to find the third. Uses V = πr²h and ρ = m/V, with unit conversions and worked steps.
Density to Weight Calculator — Convert Density × Volume to Mass | nrtechstudio.com
Free density to weight calculator: enter density and volume to get weight (mass) instantly. W = ρ × V with multi-unit support — kg/m³, g/cm³, lb/ft³, liters, gallons, cubic feet — plus a material density table (steel, water, concrete, gold). 100% in-browser, no sign-up.
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
Depreciation Calculator — 8 Methods (SL, DDB, SYD, UOP, VDB)
Free depreciation calculator: compare 8 methods (straight-line, declining balance, double declining, fixed declining, sum-of-years-digits, units of production, activity, variable declining), see the annual schedule, and learn the formulas.
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
Depth of Field Calculator — DoF, Hyperfocal, Macro, Diffraction, Crop Factor
Free depth of field calculator (DoF calculator): near/far limits and total DoF for any lens, aperture, focus distance, and sensor — plus hyperfocal distance with zone tables, macro DoF, diffraction-limited aperture by camera, 35mm-equivalent crop factor converter, and an f/1.4–f/22 aperture sweep table. 100% client-side.
Desk Size Calculator: Width, Depth & Ergonomic Height | nrtechstudio
Desk size calculator: monitor-setup width, 24-30 inch depth, ergonomic sit/stand heights, knee clearance, room fit and cable plan. Free, in + cm.
Dew Point Calculator — Magnus & Frost Point
Free dew point calculator: compute dew point from temperature & humidity (Alduchov–Eskridge 1996 Magnus formula), inverse RH, frost point below 0 °C, and fog-risk guidance from dew-point spread. °C/°F/K.
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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.