Free Date & Time Tools & Calculators
Browse 44+ free interactive date & time calculators, estimators, and utilities. 100% free, private, and runs directly in your browser without signup.
Add Business Days Calculator
Free add business days calculator — add working days to any date with custom weekends, US federal holidays, skipped-date audit trail, and Excel WORKDAY formula generator.
Add Years to Date Calculator — Future Date Adder (Free)
Free add years to date calculator: add years, months, and days to any date. Leap-year safe future date calculator — Feb 29 rolls to Feb 28, with day of week, ISO week number, quarter, and day of year. Subtract years too. 100% private, runs in your browser.
Birth from Death Date Calculator - Birth Date & Year Range
Free birth-from-death-date calculator for genealogy: estimate birth date range and birth year from a death date and age at death, with age-at-death verifier. 100% client-side.
Body Water Percentage Calculator — Watson Formula TBW | nrtechstudio.com
Body water percentage calculator using the Watson formula (Am J Clin Nutr 1980): estimate total body water in liters and as % of body weight from age,
Cheese Aging Calculator — How Long to Age Cheese (Free Planner)
Free cheese aging calculator: pick a style (cheddar, gouda, parmesan, brie, blue, swiss, camembert, monterey jack), choose an aging tier, and get your ready date, temperature & humidity targets, and a flavor timeline. 100% client-side, no signup.
Classroom Timer Suite — Visual Countdown, Interval & Noise Meter
Free online classroom timer: visual countdown, stopwatch, interval & Pomodoro timers, classroom noise meter, animated themes (bubbles, bouncing balls, calm), fullscreen projector mode, activity presets and timer queue. No sign-up.
Countdown Timer — Online Countdown to Any Date
Free online countdown timer: count down to any date or duration with quick presets, progress ring, fullscreen mode and sound alert. Accurate, no signup, 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
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.
Dutch Oven Briquette Calculator — How Many Coals on Top & Bottom | nrtechstudio
Free dutch oven briquette calculator: how many charcoal briquettes for your oven size and target temperature, top vs bottom coal split for baking, roasting, stewing and frying — plus weather adjustments, coal refresh timer and AU camp-oven mode.
Fertility by Age Calculator — Monthly Chance, 12-Month Odds & IVF Success Rates | nrtechstudio.com
Estimate monthly fecundity rate, 12-month conception chance, and IVF live-birth rates by female age. Population estimates from ASRM/ACOG data — not a
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.
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.
Hiking Time Estimator — Naismith, Langmuir, Tobler Tranter Calculator
Free hiking time calculator with elevation gain. Compare Naismith's rule, Langmuir correction, Tobler's hiking function and Tranter's fitness corrections side by side. Includes break planner, turn-back time, segment mode and metric/imperial units.
Life Path Number Calculator — Numerology Birth Date Calculator
Life path number calculator: enter your birthdate, compare simplified vs 3-cycle methods, master numbers 11/22/33, meanings, compatibility, personal y
Mechanical Advantage Calculator — Lever, Pulley, Incline & Screw | nrtechstudio
Free mechanical advantage calculator for the four simple machines: lever MA = L_in/L_out, pulley MA = rope segments n, inclined plane MA = L/h, screw
Meteor Shower Night Planner — What's Active Tonight, Peak Countdown & Best Viewing Hours
Free interactive meteor shower planner: check which meteor showers are active tonight, live countdown to peak, moon-interference score, tonight rating, and the best hours to watch — all computed in your browser.
Minutes From Now Calculator - Add or Subtract Minutes From Any Time
Free minutes-from-now calculator: add or subtract minutes or hours from any clock time (or right now) and get the exact result time with day-rollover indicator. 12h/24h toggle, duration-between-times mode, worked examples.
Mushroom Foraging Calendar: What’s in Season by Region & Month (Free)
Free interactive mushroom foraging season calendar: 28 gourmet wild mushrooms across 8 regions (Pacific Northwest, California, Northeast, Midwest, Southeast, UK, Europe, Australia). What’s fruiting now, morel season by state, species guides with lookalike warnings, printable trip checklist. 100% client-side.
ND Filter Exposure Calculator — Long Exposure Suite (Stops, Bulb Timer, Stacking, Film Reciprocity, Video)
Free ND filter exposure calculator: convert ND stops to shutter speed, stack ND8+ND64 and more, bulb countdown timer with audio cues, film reciprocity compensation (Ilford HP5+, FP4+, Kodak Tri-X, T-Max, Fuji Acros), exposure triangle rebalancer, and 180° shutter video/drone mode. 100% client-side, no data leaves your browser.
Period Calculator — Next Period Predictor & Cycle Tracker | nrtechstudio.com
Free period calculator: predict your next 6 periods from your last period date and cycle length, analyze cycle regularity from your history, see PMS windows on a 3-month calendar. 100% client-side, no signup, no app needed.
Planting Calendar 2026–2027: When to Plant Vegetables by Zone State (Free)
Free garden planting calendar by USDA zone, US state, and 30+ international regions. 67 vegetables, herbs & flowers with indoor-sow, transplant & direct-sow dates, frost dates, a what-to-plant-now planner, and print-friendly monthly view. 100% client-side — your data never leaves your browser.
Podcast Cover Art Checker — Validate, Resize & Preview (3000×3000)
Free podcast cover art checker: validate your artwork against Apple Podcasts specs (1400–3000px, square, JPG/PNG, RGB, 72dpi), one-click resize to 3000×3000, preview in Apple Podcasts / Spotify / YouTube / Pocket Casts mockups, 55px legibility test and safe-area overlay. 100% private — runs in your browser.
Pomodoro Timer — Focus Sessions Online
Free online Pomodoro timer: 25-minute focus sessions with short and long breaks, custom cycles, sound alerts and daily stats. No signup, 100% client-side.
Pregnancy Due Date Calculator — EDD by LMP, Conception, IVF & Ultrasound
Free pregnancy due date calculator: estimate your EDD from last period (Naegele's rule), conception date, IVF embryo transfer, or ultrasound dating. Get your trimester timeline, personalized week-by-week milestones, pregnancy countdown, and calendar reminders. 100% client-side, no signup.
3D Print Shrinkage & Fit Calculator — FDM Tolerance, Clearance & Hole Compensation
Free 3D print shrinkage calculator: measure your test print and get the exact slicer scale factor, plus FDM clearance recommendations (press, snug, sliding, loose), hole & pin fit compensation, and a material shrinkage database for PLA, PETG, ABS, ASA, Nylon, TPU and PC. 100% client-side — your data never leaves the browser.
Quarter Calc
Determine which fiscal quarter a date falls in.
RC Circuit Calculator — Time Constant, Charging & Discharging Curves, 555 Timer
Free RC circuit calculator: time constant tau = R·C, charging Vc(t) = V(1−e^(−t/τ)) and discharging curves with SVG plots, time-to-percentage solvers,
Rennet Dosage Calculator — How Much Rennet Per Gallon of Milk (Free)
Free rennet dosage calculator: how much rennet per gallon or litre of milk for any cheese. Cross-type converter for liquid single/double strength, tablets and powder, with cheese-style and goat/sheep milk adjustments. 100% client-side, no signup.
Soap Lye Calculator — Lye, Recipe & Mold Suite for Soap Makers
Free soap lye calculator suite: NaOH/KOH/dual-lye recipes from 200+ oils, 3 water modes, lye purity correction, citric acid, mold-to-recipe, liquid soap dilution, batch scaler, fragrance rates, quality predictions and cure dates. 100% client-side.
Spaced Repetition Planner: SM-2 Calculator, Study Schedule Forgetting Curve
Free spaced repetition planner: a verified SM-2 calculator, an exam-date study schedule generator with calendar (.ics) export, and an interactive forgetting curve visualizer. 100% client-side — your data never leaves your browser.
Stopwatch Online — Free with Lap Times
Free online stopwatch with lap times, centisecond precision, keyboard shortcuts, fastest/slowest lap highlights and CSV export. 100% client-side.
Subtract Years from Date Calculator
Free subtract years from date calculator, minus years from a date, date minus years calculator, years ago from today calculator, date calculator minus years, how to subtract years from a date, leap year date subtraction, february 29 minus 1 year handling, subtract years from date excel and edate subtract years formula guide, past date calculator years, date n years earlier calculator.
Subtitle Shifter — Fix SRT Sync: Shift Timing, Drift Resync & FPS Convert (Free)
Free online subtitle shifter: shift SRT subtitles by milliseconds, fix progressive drift with two-point resync, convert 23.976↔24↔25 fps, repair overlaps and validate SRT files. 100% client-side — your files never leave your browser.
ThreadLab — Tap Drill Calculator, Thread Identifier & 3-Wire Measurement
Free thread & tap drill suite: tap drill finder for metric (M1.6–M24), UNC/UNF (#0–1 in) with thread-percentage calculator, thread pitch identifier, three-wire pitch-diameter calculator, NPT pipe thread chart, clearance drill chart (ISO 273), and thread depth / engagement calculator. 100% client-side.
Time Since Date Calculator — Live Count-Up Timer
Free time since date calculator with a live count-up timer. See years, months, days, hours, minutes and seconds elapsed since any past date, with calendar-accurate breakdown, totals, presets and anniversary milestones.
Time Until Date Calculator — Live Countdown
Standalone live countdown calculator, time until a date, countdown to a specific date, days until calculator, how many days until, time left until date, live countdown timer to any date, countdown with months and days, shareable countdown link, new year countdown, christmas countdown.
Timecode Frame Rate Lab — Timecode Calculator, Frames to Seconds, FPS Converter
Free timecode calculator: add & subtract timecode (HH:MM:SS:FF), convert frames ↔ timecode ↔ seconds, convert between frame rates (23.976/24/25/29.97/30/50/59.94/60), plan slow motion, and understand drop-frame vs non-drop-frame. 100% free, runs in your browser.
Tree Age Calculator — Estimate Age by DBH, Circumference or Ring Count | nrtechstudio.com
Free tree age calculator: estimate a tree
Timezone Offset Calculator — Hour Difference Between Zones
Free timezone offset calculator: hour difference between any two IANA timezones on any date, with DST handled automatically. 100% client-side.
Unix Timestamp Converter — Epoch to Date & Back
Free Unix timestamp converter: epoch to date and date to epoch with live ticking clock, auto-detect seconds/ms/us/ns, ISO 8601, RFC 2822, timezone picker and batch mode. 100% client-side.
Wood Finish Coverage Calculator — How Much Stain, Polyurethane & Oil Do I Need?
Free wood finish coverage calculator: how much polyurethane, stain, Danish oil, lacquer or shellac you need for any project. Product coverage database, multi-coat planning, buy-size optimizer, wood glue mode, metric/imperial. 100% private, runs in your browser.
ADHD Planner — Free ADHD-Friendly Task Planner & Focus Timer
Free ADHD planner: brain-dump inbox, task chunker, time blocking, Eisenhower matrix and pomodoro timer. 100% private — no sign-up, runs in your browser.
Online Clock — Full-Screen Clock with Seconds, Alarm, World Clock, Stopwatch & Timer
Free online clock with seconds in full-screen: local time, date, world clock across 20+ time zones, alarm clock, stopwatch with laps, and countdown timer. No download, no sign-up.
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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.