Free Online Tools
Simple, fast, and private. Every tool runs entirely in your browser — no signup, no data collection, no nonsense.
Popular tools
Mortgage Calculator
Calculate monthly payments, compare loan terms, and see a full cost breakdown — free, no signup required
Compound Interest Calculator
Calculate future value, total interest earned, and see year-by-year growth with visual charts — free, no signup required
W-4 Withholding Calculator
Optimize your W-4 form to get the right amount withheld from each paycheck — avoid a big tax bill or an oversized refund
401(k) Retirement Calculator
Project your 401(k) balance at retirement with employer match, catch-up contributions, and year-by-year growth charts
Tax Bracket Calculator
Calculate your 2025 US federal income tax by bracket — see exactly how much tax you owe in each bracket, your effective rate, and your marginal rate
BMI Calculator
Calculate your Body Mass Index instantly, see your BMI category, healthy weight range, and track changes over time
TDEE Calculator
Calculate your Total Daily Energy Expenditure, BMR, and macros for weight loss, maintenance, or muscle gain
Macro Calculator
Calculate your daily protein, carbs, and fat targets based on your body stats, activity level, and diet goal
Free Invoice Generator
Create professional invoices and download as PDF — no signup required
Paycheck Calculator
Calculate your exact take-home pay after federal taxes, state taxes, FICA, and pre-tax deductions — free, private, no signup
JSON Formatter & Validator
Format, validate, minify, and explore JSON data with syntax highlighting and tree view
Salary to Hourly Converter
Convert between annual salary and hourly rate instantly with overtime, vacation, and currency support
Net Worth Calculator
Add your assets and liabilities to instantly calculate your net worth — free, private, no signup required
A1C to Average Blood Sugar Calculator
Convert between A1C percentage and estimated average glucose (eAG) in mg/dL and mmol/L
ARV Calculator
Calculate After-Repair Value and Maximum Allowable Offer using the 70% rule — free real estate investing tool
Safe Withdrawal Rate Calculator
Calculate how long your portfolio will last at different withdrawal rates and see the required portfolio size for your retirement income.
Browse by category
3D Printing
28Free 3D printing calculators for FDM and SLA/MSLA. Estimate...
Agriculture
38Free agriculture calculators for crop yield estimation, seed...
Automotive Calculators
65Free automotive calculators for lease vs buy, EV savings,...
Beauty
32Free beauty and skincare calculators. Hair porosity quiz,...
Brewing
33Free homebrewing calculators for beer, mead, and cider. IBU,...
Business
128Free business calculators for invoicing, profit margins,...
Career
68Free career tools for salary comparison, meeting cost...
Cheatsheets
39Free printable cheatsheets and quick reference cards....
Checklists
39Free interactive checklists for travel, moving, projects,...
Comparisons
41Free comparison tools for making informed decisions. Compare...
Converters
52Free converters for units, binary/hex, Roman numerals, text...
Crafts
75Free tools for musicians, photographers, and crafters. Chord...
Developer
289Free developer tools for JSON formatting, regex testing,...
Disc Golf
10Free disc golf calculators for handicap, player ratings,...
Education
82Free education tools for GPA calculation, grade scales,...
Electronics
37Free electronics calculators for hobbyists, students, and...
Events
52Free event planning tools for weddings, catering, budgets,...
Fitness
135Free fitness calculators for protein intake, TDEE, running...
Food & Cooking
95Free cooking calculators for measurement conversions, recipe...
Food Business
12Free food truck and restaurant business calculators....
Gaming
54Free gaming calculators and tools for D&D, tabletop RPGs,...
Garden
86Free garden calculators for planting schedules, composting,...
Guides
33Free interactive guides and step-by-step tools. Learn...
Health
83Free health and fitness calculators for BMI, TDEE, macros,...
History
19Free history tools for timelines, date calculations,...
Home Improvement
148Free home improvement calculators for drywall, roofing,...
Houseplants
19Free houseplant care calculators for watering schedules,...
Insurance
41Free insurance calculators for health, life, auto, home,...
Investing
98Free investment calculators for compound interest, FIRE...
Legal
47Free legal calculators for injury settlements, child...
Map & Geography
18Free map and geography tools for coordinate conversion,...
Math
49Free online math calculators for algebra, statistics,...
Medical
51Free medical calculators for IV drip rates, Glasgow Coma...
Music
46Free music tools for musicians and producers. Tap tempo BPM...
Numerology
22Free numerology and astrology calculators. Find your life...
Outdoors
61Free outdoor calculators for sunrise/sunset times, wind...
Parenting
38Free parenting calculators for baby growth percentiles,...
PDF Tools
27Free browser-based PDF tools: merge, split, compress,...
Pets
69Free pet calculators for dogs, cats, horses, and fish. Age...
Photography
38Free photography calculators for depth of field, exposure...
Real Estate
61Free real estate calculators for mortgages, rent vs buy...
Reference
79Free reference tools with lookup tables, data charts, and...
RV
27Free RV and van life calculators for solar panel sizing,...
Science
89Free online science calculators for physics, chemistry, and...
Subtitles
10Free online subtitle tools: convert SRT to VTT, shift...
Sustainability
31Free sustainability calculators to measure your carbon...
Tax
92Free online tax calculators for W-4 withholding,...
Tests & Quizzes
66Take free online quizzes and self-assessment tests....
Timelines
34Free timeline generators and progress visualization tools....
Travel
45Free travel tools for Schengen visa calculations, timezone...
Utilities
90Free utility tools for date calculations, WiFi QR codes,...
Woodworking
28Free woodworking calculators for board feet, dovetails,...
Writing
81Free writing tools for word counting, AI prompt building,...
Why people trust our tools
100% Free
No hidden fees, no premium tiers, no tricks. Every feature of every tool is completely free to use, forever.
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Everything runs in your browser. We never see your data, never store it, and never share it with anyone.
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Use any tool instantly. No account needed, no email required, no forms to fill out. Just open and start using.
What You Can Do With FastTools
FastTools brings together over 3130 free calculators, converters, reference guides, and interactive tools organized by what you are trying to accomplish.
Managing your finances? The tax calculators cover W-4 withholding, tax brackets, and estimated quarterly payments. The investing tools handle compound interest, portfolio allocation, 401k projections, and retirement planning. If you are buying or selling property, the real estate calculators include mortgage payment, closing costs, and rent-vs-buy comparisons. Running a business? The business tools cover invoice generation, break-even analysis, payroll, and markup calculations. Need to check your insurance coverage? There are calculators for life insurance, home insurance estimates, and deductible comparisons.
Working on your health or fitness? The health calculators include BMI, calorie needs, body fat percentage, and macro ratios. The fitness tools help with one-rep max, training volume, and pace calculations. The food and nutrition tools cover cooking conversions, recipe scaling, and calorie lookups. The medical calculators cover dosage, BMR, and clinical scoring tools.
Getting professional work done? The developer tools cover cron expressions, color contrast, regex testing, JSON formatting, and base64 encoding. The PDF tools handle merging, splitting, redacting, annotating, and OCR. Writing tools for word count, readability, and script timing. Planning your career? Salary negotiation, raise calculators, and freelance rate tools.
Working on something around the house? The home improvement calculators handle paint coverage, flooring estimates, and material quantities. The garden tools cover soil volume, fertilizer ratios, and planting schedules. The automotive tools include fuel economy, towing capacity, and depreciation calculators.
For everything else — the converters, reference guides, and utilities cover day-to-day calculations that don't fit a single niche.
All calculations run locally in your browser. No data is sent to any server. Every tool does one thing well — no signup, no premium tier, no tracking.