156 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.
Health
BMI, BMR, TDEE, GFR, clinical scores, dosing, and wellness calculators
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.)
OpenDevelopers
JSON, JWT, IPv4/CIDR, password entropy, bandwidth, regex, and more
JSON 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
OpenText
Word counter, case conversion, URL/HTML encode, slug generator
Word 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
OpenFinance
NPV, IRR, mortgage, sales tax, break-even, Gordon model, and savings
Compound 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
OpenMath
Equations, matrices, statistics, regression, probability, and geometry
Quadratic 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)
OpenDate & Time
Age, date difference, ISO week number, and countdown tools
Fitness
Wilks, VDOT, 1RM, Cooper test, Karvonen zones, and calorie cycling
Designers
Color palettes, image compression, golden ratio, and aspect ratio crop
Marketers
QR codes, meta tags, UTM link builder, and campaign tools
Traders
Kelly criterion, expectancy, risk of ruin, pip value, and position sizing
Position 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
OpenEngineering
Reynolds number, beam deflection, pumps, Hooke's law, Euler buckling
Reynolds 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
Education
Weighted GPA, exam grades, spaced repetition, and study planning
Veterinary
Pet age in human years and daily food portion calculator
Legal
Contract late fees, statute of limitations, post-judgment interest, court fees
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
OpenAutomotive
Trip cost, EV range, braking distance, tire speedometer error, and TCO
Photo & Video
DOF, EV, FOV, diffraction limit, shutter angle, and video bitrate
Aspect 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
OpenReal Estate
Buy vs rent, DSCR, refinance, cash flow, rental yield, and flip profit
General
Password generator, Roman numerals, electricity cost, and everyday utilities