200 free tools
Useful tools for everyone
JSON formatters, QR codes, calculators, converters — everything runs right in your browser. No signup, no data sent to a server.
BMI Calculator
Body mass index and weight category
OpenBMR Calculator
Basal metabolic rate (Mifflin-St Jeor formula)
OpenTDEE Calculator
Daily calorie needs based on activity level
OpenCalorie Deficit
Time to reach target weight
OpenIdeal Weight
Devine formula estimate
OpenBody Fat % (Navy)
US Navy circumference method
OpenMacro Calculator
Protein, fat, and carbs from calories
OpenHeart Rate Zones
Training heart rate zones
OpenBlood Alcohol Calculator
Estimated blood alcohol concentration
OpenDue Date
Estimated due date from last menstrual period
OpenSleep Cycle Calculator
Optimal wake times based on sleep cycles
OpenWaist-to-Hip Ratio
WHR index and risk assessment
OpenBody Surface Area
Mosteller formula (m²)
OpenCalorie Burn
Calories burned by MET and duration
OpenBlood Pressure
Blood pressure category
OpenGFR (CKD-EPI 2021)
Estimated glomerular filtration rate from creatinine
OpenCreatinine Clearance
Cockcroft-Gault formula
OpenBSA-Based Dose
Drug dose based on body surface area
Openmg/kg Dose
Total dose = dose per kg × body weight
OpenPediatric Dose
Young's and Clark's rules from adult dose
OpenCorrected QT (QTc)
QTc by Bazett: QT / √RR
OpenAnion Gap
AG = Na − (Cl + HCO₃)
OpenMean Arterial Pressure (MAP)
MAP = DBP + (SBP−DBP)/3
OpenMaintenance Fluids
Holliday-Segar: mL/day by weight
OpenParkland Formula
Burn resuscitation: 4 mL × kg × %TBSA
OpenCHA₂DS₂-VASc
Stroke risk in atrial fibrillation
OpenWells DVT
Deep vein thrombosis probability
OpenGlasgow Coma Scale
GCS: eye + verbal + motor response
OpenIdeal Body Weight (Devine)
For dosing calculations (aminoglycosides, etc.)
OpenWater Intake Calculator
Daily water needs from body weight and activity
OpenJSON Formatter
Format, minify, and validate JSON in your browser
OpenJWT Decoder
Decode JWT tokens locally — nothing is sent to a server
OpenBase64 Encode/Decode
Encode and decode text with Base64
OpenCron Expression Builder
Build and explain cron schedules
OpenUUID Generator
Generate cryptographically random UUID v4 values
OpenTimestamp Converter
Convert Unix timestamps to dates and back
OpenHash Generator
SHA-256, SHA-384, and SHA-512 hashing in the browser
OpenRegex Tester
Test JavaScript regular expressions against sample text
OpenSubnet Calculator
Number of usable hosts
OpenIPv4 Range
Network, broadcast, and hosts from CIDR
OpenTransfer Time
File transfer time from link speed
OpenPassword Entropy
Strength in bits from character set
OpenCSS clamp() Helper
Build a fluid clamp() from min, preferred, and max sizes
OpenWord Counter
Count words, characters, and reading time
OpenUPPERCASE
Convert text to all uppercase letters
Openlowercase
Convert text to all lowercase letters
OpenTitle Case
Capitalize the first letter of each word
OpenSort Lines
Sort lines alphabetically (A–Z)
OpenRemove Duplicate Lines
Keep only unique lines of text
OpenURL Encode
Percent-encode text for URLs (encodeURIComponent)
OpenURL Decode
Decode percent-encoded URL text
OpenHTML Encode
Escape special HTML characters
OpenHTML Decode
Unescape HTML entities back to plain text
OpenSlug Generator
Create URL-friendly slugs from text
OpenLorem Ipsum Generator
Generate placeholder paragraphs for mockups
OpenCompound Interest Calculator
Future value with annual compounding
OpenLoan Payment Calculator
Monthly payment on a fixed-rate loan
OpenSales Tax Calculator
Add or extract sales tax from a price
OpenTip Calculator
Calculate tip and split the bill at a restaurant
OpenInflation Calculator
Purchasing power loss over time
OpenBreak-Even Calculator
Units needed to cover fixed and variable costs
OpenNPV Calculator
Net present value of cash flows
OpenIRR Calculator
Internal rate of return (Newton's method)
OpenMortgage Extra Payment Calculator
Compare payoff time with extra principal payments
OpenAnnuity Future Value
Future value of monthly contributions plus initial deposit
OpenGordon Growth Model
Stock valuation using dividend discount model
OpenPayback Period Calculator
Simple and discounted payback period
OpenDiscount Calculator
Sale price, savings, and original price from a discount
OpenROI Calculator
Return on investment as a percentage and multiple
OpenQuadratic Equation
ax² + bx + c = 0, discriminant and roots
Open2×2 Linear System
Solve using Cramer's rule
Open3×3 Determinant
Expansion along the first row
Open2×2 Eigenvalues
Characteristic polynomial
OpenCombinatorics
C(n,k), P(n,k), and n!
OpenBayes' Theorem
P(A|B) from prior probabilities
OpenBinomial Distribution
P(X=k) for n trials
OpenZ-Score and Percentiles
Standardization and P(Z ≤ z)
OpenDescriptive Statistics
Mean, median, σ for a sample
OpenLinear Regression
y = a + bx, R² by OLS
OpenConfidence Interval
CI for the mean (t≈z)
OpenTriangle Solver
SSS or SAS — sides and angles
OpenLogarithmic Equation
Find x where bˣ = c
OpenGeometric Series Sum
Sₙ given a₁, r, and n
OpenProbability AND / OR
Independent and mutually exclusive events
Open3D Distance
Between points (x,y,z)
OpenPercentage Calculator
Find X% of Y, what percent X is of Y, and percentage change
OpenAge Calculator
Exact age from date of birth
OpenDate Difference
Days between two dates
OpenWeek Number
ISO week of the year
OpenCountdown Calculator
Days, hours, and minutes remaining until a target date
OpenBusiness Days Calculator
Weekdays between two dates (excludes weekends)
OpenAdd / Subtract Dates
Add or subtract days, weeks, or months from a date
OpenWork Hours Calculator
Hours worked between two times, with break deduction
OpenTimezone Offset Converter
Convert a local time between UTC offsets
OpenDays Until Calculator
Countdown in days to a future event date
Open1RM
One-rep max (Epley formula)
OpenVO2max (Cooper)
Cooper 12-minute run test
OpenWilks Score
Compare powerlifting totals by body weight
OpenVDOT / Daniels
VO2max from race result
OpenKarvonen Heart Rate
Training zones from HRmax and HRrest
OpenCalorie Cycling
Alternate high/low calorie days
OpenRunning Pace Calculator
Pace, speed, and finish time from distance and time
OpenColor Palette Generator
Generate a 5-shade palette from a base color
OpenImage Compressor
Compress JPEG and WebP images locally
OpenGolden Ratio
Major and minor segments
OpenContrast Checker
WCAG contrast ratio between two hex colors
Openpx ↔ rem Converter
Convert pixels to rem and back at any root font size
OpenType Scale Generator
Modular typography scale from a base size and ratio
OpenHEX ↔ RGB Converter
Convert hex colors to RGB and back
OpenSpacing Scale
Consistent spacing steps from a base unit
OpenQR Code Generator
Create downloadable QR codes for URLs and text
OpenMeta Tags Generator
Generate Open Graph and Twitter Card HTML
OpenUTM Builder
Build campaign URLs with UTM parameters
OpenROAS Calculator
Return on ad spend and profit from campaign results
OpenCTR / CPC / CPA Calculator
Click-through rate, cost per click, and cost per acquisition
OpenA/B Test Significance
Two-proportion z-test for conversion experiments
OpenAd Budget Pacing
Daily spend needed to hit a campaign budget on time
OpenEngagement Rate Calculator
Engagement rate from likes, comments, shares, and reach
OpenPosition Size Calculator
Calculate trade size based on risk and stop-loss
OpenPip Value
Forex pip value per lot
OpenKelly Criterion
Optimal fraction of capital per trade
OpenTrade Expectancy
E = WR×AvgWin − LR×AvgLoss
OpenRisk of Ruin
Approximation for fixed risk fraction
OpenFutures Position Size
Contracts by risk and stop in ticks
OpenReynolds Number
Re = v·L/ν — flow regime (laminar / turbulent)
OpenBeam Deflection (Center)
Simply supported beam, point load: δ = PL³/(48EI)
OpenBeam Moment (Uniform Load)
Simply supported beam, uniform load: M_max = qL²/8
OpenCantilever Beam
Point load at free end: δ = PL³/(3EI)
OpenAxial Stress
σ = F/A and factor of safety
OpenPipe Flow Velocity
v = Q / A from flow rate and diameter
OpenPump Power
P = ρgQH / η
OpenHeat Conduction
Steady-state: Q = k·A·ΔT / L
OpenPower and Torque
P = T·n / 9550 (kW, N·m, rpm)
OpenGear Ratio
Output speed and torque of gearbox
OpenDynamic Pressure
q = ½ρv² and head v²/(2g)
OpenHooke's Law
σ = E·ε, ε = ΔL/L
OpenHydraulic Cylinder
F = p·A, A = πD²/4
OpenShell Thickness
Thin-walled vessel: t = PR/(S·E − 0.6P)
OpenEuler Critical Load
P_cr = π²EI / (KL)²
OpenConstruction
Concrete, tile, board feet, roof pitch, insulation R-value, and stairs
View all 11 tools →Unit Converter
Convert length, weight, area, and volume units
OpenConcrete Volume
For a slab
OpenTile Calculator
Number of tiles needed
OpenBoard Feet
Lumber volume
OpenRoof Pitch
Pitch and angle
OpenInsulation Thickness
From R-value
OpenStair Calculator
Number of steps
OpenPaint Coverage Calculator
Gallons or liters of paint needed for a room
OpenDrywall Calculator
Number of 4×8 sheets for walls and ceiling
OpenGravel / Aggregate Calculator
Tons and cubic yards of gravel for a pad or path
OpenFence Post Calculator
Posts, rails, and panels for a straight fence run
OpenLegal
Contract late fees, statute of limitations, post-judgment interest, court fees
View all 6 tools →Contract Late Fee Calculator
Daily late fee based on contract rate and days overdue
OpenAnnual Late Fee Calculator
Late fee from an annual percentage rate
OpenLate Fee Cap Checker
Check if accrued late fees exceed a contract cap
OpenStatute of Limitations Estimator
Estimate the deadline to file a civil claim
OpenPost-Judgment Interest Calculator
Interest on a judgment using an annual rate
OpenCourt Filing Fee Estimator
Approximate federal district court civil filing fee
OpenAspect Ratio Crop
Calculate center-crop dimensions for any aspect ratio
OpenShutter Angle
Shutter angle from FPS and exposure time
OpenDepth of Field
Near/far DOF and hyperfocal distance
OpenExposure Value (EV)
EV and exposure at given ISO
OpenField of View
Horizontal FOV from sensor size
OpenDiffraction Limit
Max f/ before sharpness loss
OpenVideo Bitrate
H.264/H.265 with overhead and audio
OpenRecipe Scaler
Scale ingredient amounts up or down by servings
OpenCooking Unit Converter
Convert cups, tablespoons, teaspoons, ml, and grams
OpenBaker's Percentage
Flour-relative percentages for bread formulas
OpenOven Temperature Converter
Convert °F ↔ °C for oven settings
OpenCooking Time by Weight
Scale roast or turkey time from weight
OpenAlcohol Dilution Calculator
Water needed to dilute spirits to a target ABV
OpenRecipe Cost Calculator
Cost per serving from ingredient costs
OpenPasta Water Ratio
Water and salt for boiling pasta
OpenSalary & Taxes
Hourly ↔ salary, raises, overtime, contractor rates, and take-home estimates
View all 8 tools →Hourly to Salary Converter
Convert hourly wage to weekly, monthly, and annual pay
OpenSalary to Hourly Converter
Convert annual salary to an equivalent hourly rate
OpenRaise Calculator
New salary and percent increase from a raise
OpenOvertime Pay Calculator
Weekly pay with time-and-a-half overtime
OpenContractor Day Rate
Day and hour rates from a target annual income
OpenTake-Home Pay Estimator
Rough US take-home after federal income tax and FICA
OpenCommission Calculator
Earnings from base salary plus sales commission
OpenSeverance Estimator
Rough severance from weeks-per-year of service
OpenGeneral
Password generator, Roman numerals, electricity cost, and everyday utilities
View all 4 tools →