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.
CTR Calculator: Ad Click-Through Rate (Free)
Free CTR calculator: compute click-through rate from clicks and impressions, inverse clicks/impressions solver, compare two campaigns, and see an illustrative benchmark table per channel. 100% client-side.
Cube Density Calculator — Mass, Volume & Density
Free cube density calculator: enter any two of mass, side length, or density to find the third. Density of a cube formula ρ = m / s³, with unit conversions and worked steps.
Cube Volume Calculator: V = s3, Side From Volume, Surface Area
Free cube volume calculator. Compute volume of a cube from side length (V = s cubed), or find the side from volume with the cube root. Bonus: surface area (6s squared), space diagonal (s times root 3), unit conversions to liters, gallons, cubic feet, and a labeled cube diagram.
Perfect Cubes Calculator — Checker, List 1-100 & Nearest Cube
Free perfect cubes calculator: check if any number is a perfect cube, browse the table of perfect cubes 1^3 to 100^3 with gap patterns, and find the nearest perfect cube above or below any number. Exact integer math, no signup.
Cubic Equation Calculator - Solve ax^3+bx^2+cx+d=0 (Cardano's Method)
Free cubic equation calculator: solve ax^3+bx^2+cx+d=0 with Cardano's method. Shows all 3 roots (real or complex), discriminant analysis, casus irreducibilis trigonometric form, step-by-step working a
Cubic Feet Calculator
Free cubic feet calculator: box and room volume, cylinder volume, multi-room project totals, ft3 to yd3/gallons/liters converter, and soil/mulch/gravel bag estimator.
Cubic Feet to Gallons Converter (US and Imperial)
Convert cubic feet to gallons and back. 1 cubic foot = 7.48051948 US gallons or 6.22883546 imperial gallons. Free ft3 to gallon calculator with formula, quick table, and aquarium and pool examples.
Cubic Feet to Pounds Converter: Weight Calculator with Density Table
Free cubic feet to pounds calculator. Convert cubic feet to pounds using material density (water, concrete, soil, sand, gravel, steel) or a custom lb/ft3 value. Includes cubic feet to tons, a pounds per cubic foot chart, and the cubic foot to pounds formula.
Cubic Inches Calculator: in³ to mL, Liters, Cubic Feet, Gallons
Free cubic inches calculator. Convert in³ to mL, cc, liters, cubic feet, US and imperial gallons, two ways. Exact factor 1 in³ = 16.387064 mL, plus engine displacement (CID to liters) examples.
Cubic Meter to Ton Converter | m3 to Tons Weight Calculator
Free cubic meter to ton calculator. Convert cubic meters (m3) to metric tons, kilograms, US tons and pounds using material density (water, concrete, sand, gravel, soil, steel) or a custom kg/m3 value. Includes a bulk density chart and a quick m3 to ton table.
Cubic Yards to Tons Calculator: Convert yd3 to US Tons, lb, kg and Tonnes
Free cubic yards to tons calculator. Convert yd3 to US tons, pounds, kilograms and metric tonnes for topsoil, gravel, sand, mulch, concrete and 20 materials, plus a quick tons-per-cubic-yard chart and dumpster weight guide.
Cuboid Surface Area Calculator — Two-Way + Volume & Space Diagonal
Calculate cuboid surface area SA = 2(lw + lh + wh), volume, and space diagonal. Reverse mode: find the third dimension from surface area. Unit conversion mm–mi. Free.
Cups to Quarts Converter
Free cups to quarts converter with US liquid, imperial, and US dry modes. Convert cups to quarts or quarts to cups instantly, plus quick conversion charts and cooking measurement context.
cURL GET Request Generator
Interactive cURL GET request builder with query parameters, headers, bearer token auth, and code export.
cURL HEAD Request Generator & Inspector
Generate cURL HEAD commands and analyze HTTP response headers, redirect chains, and security headers online.
Curl Online
cURL POST Request Generator
Interactive cURL POST request builder supporting JSON payloads, form-data, multipart uploads, and language code export.
cURL to JavaScript Converter
Convert cURL CLI commands into clean modern JavaScript code for Fetch API, Axios, and Node.js.
Curl To Python
Currency Formatter - Format Numbers as Money in 60+ Currencies
Free currency formatter: format numbers as money in 60+ currencies with correct symbols, decimals and locale separators. Batch mode, copy button.
Tool - Currency Converter & Money Conversion Calculator
Real-time global currency to converter, foreign exchange calculator, bank fee spread analysis, and multi-currency money conversion matrix.
Current Divider Calculator - Branch Currents for Parallel Resistors
Free current divider calculator: split total current across 2, 3 or n parallel branches (I1 = It·R2/(R1+R2)), plus a resistor design solver. 100% client-side, no sign-up.
Curtain Fabric Calculator — How Much Fabric for Curtains? (Free)
Free curtain fabric calculator: find exactly how much fabric you need for curtains. Yardage by pleat type (pinch, grommet, rod pocket, tab top), fullness ratio, pattern repeat matching. Metric + imperial.
Curtain Size Calculator — What Size Curtains Do I Need? (Free)
Free curtain size calculator: what size curtains do I need? Panel width, rod length, hanging height and finished length. Imperial + metric, 7 modes.
Customer Effort Score (CES) Calculator — Compute CES 1–7
Free Customer Effort Score (CES) calculator: compute average CES on a 1–7 scale, see response distribution, compare two periods, and understand score interpretation. 100% in-browser.
Cutoff Frequency Calculator — RC & RL Filters (fc = 1/(2πRC))
Free cutoff frequency calculator for RC and RL low-pass / high-pass filters. Compute fc = 1/(2πRC) or fc = R/(2πL), time constant, -3 dB point, phase shift, and see a Bode magnitude plot.
Cv Flow Coefficient Calculator — Valve Sizing (Liquid & Gas)
Free Cv flow coefficient calculator for valve sizing: liquid Cv = Q×√(SG/ΔP), gas Cv with choked-flow detection, reverse solvers for flow rate and pressure drop, Cv to Kv converter, and typical valve Cv charts. 100% client-side, no signup.
CVD Risk Calculator — 10-Year Framingham Risk Score
Free 10-year CVD risk calculator using the Framingham General CVD Risk Score (D'Agostino 2008): enter age, cholesterol, blood pressure, smoking and diabetes to get your points, 10-year risk % and risk category. 100% in-browser. Educational tool — not medical advice.
CVSS Calculator — v4.0, v3.1, v3.0 v2.0 Score Calculator (Free, Client-Side)
Free CVSS calculator for all versions — v4.0, v3.1, v3.0 and v2.0 — on one page. Paste a CVSS vector string or click metrics to get the base, temporal and environmental scores instantly. 100% client-side: nothing leaves your browser.
Cycling Power Zones Calculator — FTP Zones (Coggan 7-Zone) + LTHR Heart Rate Zones
Free cycling zones calculator: enter your FTP to get all 7 Coggan power zones in watts, or enter LTHR for cycling-specific heart rate zones. 100% client-side.
Cyclotron Frequency Calculator - f = qB/(2πm), Magnet Designer & Mass-to-Charge Solver
Free cyclotron frequency calculator: f = qB/(2πm) for electron, proton, deuteron, alpha and custom ions. Solve magnet field B from target frequency, mass-to-charge m/q, angular frequency ω and period
D&D Name Generator & 5e Character Lore Maker
Interactive D&D name generator, human name generator DnD 5e, fantasy lore creator, and character background builder.
Damping Ratio (ζ) Calculator — Log Decrement & Overshoot
Free damping ratio calculator ζ = c/(2√(k·m)): under/critical/overdamped classification, damped frequency ω_d, logarithmic decrement δ, percent overshoot, and damper design c from target ζ. 100% client-side.
Darcy-Weisbach Calculator — Pipe Friction Head Loss (Colebrook) | nrtechstudio.com
Free Darcy-Weisbach head loss calculator. Enter pipe length, diameter, flow velocity or flow rate — get hf = f(L/D)(v²/2g) with the friction factor solved from the Colebrook equation, Reynolds number, minor losses, and pressure drop in kPa/psi. 100% in-browser, no sign-up.
Darcy’s Law Calculator — Groundwater Discharge (Q = k·A·i)
Darcy’s law calculator for groundwater flow: compute discharge Q, hydraulic conductivity k, hydraulic gradient i, Darcy velocity, and true pore velocity. Includes k unit conversion and intrinsic permeability.
OSHA DART Rate Calculator — Days Away, Restricted or Transferred
Compute workplace-safety DART rate and TRC rate with the OSHA formula: (case count × 200,000) / total hours worked. Includes an industry-average comparator and an explanation of the 200,000 figure.
Data Conversion Calculator & Computer File Size Studio
Interactive data conversion calculator and computer file size calculator across binary KiB/MiB/GiB and decimal KB/MB/GB storage.
Data Rate Converter — Mbps, Gbps, MB/s, Bits vs Bytes (SI + IEC)
Free data rate converter: Mbps, Gbps, Kbps, bps to MB/s, GB/s and honest IEC Mibps units. Live two-way, download-time estimator, bits-vs-bytes guide. 100% client-side.
Data Storage Converter — Bytes, KB, MB, GB, TB, GiB
Free online data storage converter: convert bits, bytes, KB, MB, GB, TB, PB and binary KiB, MiB, GiB, TiB, PiB, plus a download transfer-time estimator. 100% client-side.
Data Usage Calculator
Data usage calculator: estimate monthly GB for Netflix, YouTube, Spotify, Zoom & gaming with official bitrates. Check data caps & overage cost
Date Difference Calculator & Days Between Dates
Standalone date difference calculator, calculate dates between two dates, date difference in days, difference between two dates in days, date difference calculator in days, date count between two dates, dates between two dates, between two dates calculator, difference between two dates, days between two dates calculator, and number of days between two dates.
Date to Roman Numerals Converter — Write Any Date in Roman Numerals (Free)
Free date to Roman numerals converter: turn any calendar date into Roman numerals (VII.X.MMXXVI), with show-your-work steps, Latin month names, decode mode, and copy. 100% client-side — your dates never leave the browser.
Days From Date Calculator - Add or Subtract Days, Weeks, Months
Free days-from-date calculator: add or subtract days, weeks or months from any date and get the exact result date plus day of the week. Includes a reverse days-between mode and worked examples.
Days Inventory Outstanding (DIO) Calculator — Inventory Days
Compute days inventory outstanding (DIO): DIO from inventory & COGS, target-DIO solver to maximum inventory, inventory-reduction simulator, and DIO benchmark table by sector. 100% in-browser.
DPO (Days Payable Outstanding) Calculator
Free DPO calculator: compute days payable outstanding from average accounts payable and COGS, find the ideal accounts payable balance for a DPO target, and simulate the impact of extending payment terms. 100% client-side.
Days to Months Converter: Convert Days to Months Online
Free days to months calculator. Convert days to months with 3 methods: average month (30.44 days), exact calendar month, or simple 30-day month. Includes days to months chart, formula, and reverse months to days converter.
Days to Weeks Converter: Convert Days to Weeks Instantly
Free days to weeks calculator. Convert days to weeks with decimals, or see weeks and days breakdown. Also converts weeks back to days. Exact 1 week = 7 days.
Days to Years Converter: Convert Days to Years Instantly
Free days to years calculator with 3 year lengths: 365, 365.25, and 365.2422 days. Convert days to decimal years, see the years and days breakdown, and convert years back to days. Explains Google's 0.00273790926 answer.
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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.