Developer Utilities
Small developer utilities that save a trip to a random website. Encode and decode Base64, explain a regex, build UTM links, generate QR codes and vCards, and more — the everyday helpers. Free in your browser, and available by API when you need them in a script.
Developer Utilities
Calculate property cap rate from NOI and market value
POST /realestate/capitalization-rate$0.002Developer Utilities
Calculate Annual HOA Fee Total from Monthly or Quarterly Dues
POST /realestate/hoa-fee-annual-total$0.002Developer Utilities
Calculate PMI removal threshold from home value and loan balance
POST /realestate/pmi-threshold-calc$0.002Developer Utilities
Annual property tax calculator
assessed value and local rate
POST /realestate/property-tax-estimate$0.002Developer Utilities
Calculate refinance break-even months from costs and savings
POST /realestate/refinance-breakeven$0.002Developer Utilities
Calculate room square footage from length and width
POST /realestate/square-footage-from-dimensions$0.002Developer Utilities
Estimate utility cost per square foot
property calculator
POST /realestate/utility-cost-per-sqft$0.002Developer Utilities
Validate API key format
check prefix, length and charset
POST /security/api-key-format-validate$0.002Developer Utilities
CORS header configuration checker
find credential and Vary issues
POST /security/cors-header-check$0.002Developer Utilities
Check File Extension Risk Level for Email Attachments
POST /security/file-extension-risk-check$0.002Developer Utilities
Map data fields to GDPR categories and special-category flags
POST /security/gdpr-data-category-map$0.002Developer Utilities
Compare hash algorithm output length and collision security
POST /security/hash-algorithm-compare$0.002Developer Utilities
Build an HSTS header value
max-age, subdomains, and preload
POST /security/hsts-header-build$0.002Developer Utilities
TOTP time window calculator
seconds remaining and window index
POST /security/otp-time-window-calc$0.002Developer Utilities
Classify data fields as PII
direct, indirect, or non-PII
POST /security/pii-field-classify$0.002Developer Utilities
Parse rate-limit response headers and calculate reset time
POST /security/rate-limit-header-parse$0.002Developer Utilities
Estimate secure delete overwrite passes for SSD or HDD
POST /security/secure-delete-passes-estimate$0.002Developer Utilities
Format an SSH key fingerprint as colon hex or Base64
POST /security/ssh-key-fingerprint-format$0.002Developer Utilities
Check whether a TLS version is still supported
POST /security/tls-version-support-check$0.002Developer Utilities
Seeded two-factor backup code generator
POST /security/two-factor-backup-codes-generate$0.002Developer Utilities
Webhook signature verification steps
build a safe HMAC receiver
POST /security/webhook-signature-verify-steps$0.002Developer Utilities
Cash denomination calculator
minimum bills and coins, free
POST /travel2/currency-cash-denomination-split$0.002Developer Utilities
Frequent flyer miles value calculator
cents per mile
POST /travel2/frequent-flyer-miles-value$0.002Developer Utilities
Hotel price per night calculator
compare total stay prices fairly
POST /travel2/hotel-price-per-night-compare$0.002Developer Utilities
Check itinerary time conflicts and overlapping activities
POST /travel2/itinerary-time-conflict-check$0.002Developer Utilities
Estimate jet lag adjustment days
eastward or westward
POST /travel2/jet-lag-adjustment-days$0.002Developer Utilities
Check passport validity for a travel date
six-month rule
POST /travel2/passport-expiry-travel-check$0.002Developer Utilities
Road trip fuel stop calculator
intervals and stops
POST /travel2/road-trip-fuel-stops$0.002Developer Utilities
Affiliate Commission Calculator for Tiered Payouts
POST /ecom/affiliate-commission-calc$0.002Developer Utilities
Dropshipping profit per order calculator
POST /ecom/dropship-profit-calc$0.002Developer Utilities
Free shipping threshold calculator
find the amount left to spend
POST /ecom/free-shipping-threshold-gap$0.002Developer Utilities
Calculate Inventory Turnover Ratio and Days to Sell Through
POST /ecom/inventory-turnover-ratio$0.002Developer Utilities
Check A/B test sample size adequacy and conversion significance
POST /ecom/landing-page-ab-test-significance$0.002Developer Utilities
Marketplace Fee Calculator
Calculate Your Net Seller Payout
POST /ecom/marketplace-fee-net-calc$0.002Developer Utilities
Product Bundle Discount Calculator
Price and Savings
POST /ecom/product-bundle-discount$0.002Developer Utilities
Calculate product return rate from units sold and returned
POST /ecom/return-rate-calculate$0.002Developer Utilities
Calculate weighted average product rating from star counts
POST /ecom/review-rating-average$0.002Developer Utilities
Subscription plan change proration calculator
credit and charge
POST /ecom/subscription-proration-calc$0.002Developer Utilities
Ten-Pin Bowling Score Calculator by Frame
POST /game/bowling-score-calculate$0.002Developer Utilities
Seeded Standard Card Deck Shuffle
Reproducible 52-Card Order
POST /game/card-deck-shuffle-seeded$0.002Developer Utilities
Darts Checkout Calculator
Suggest a Three-Dart Finish
POST /game/dart-score-checkout$0.002Developer Utilities
Parse D&D dice notation
count, sides, modifier and roll range
POST /game/dnd-dice-notation-parse$0.002Developer Utilities
Elo Rating Update Calculator
New Ratings After a Match
POST /game/elo-rating-update$0.002Developer Utilities
Poker Hand Ranking Calculator
Check Five-Card Strength
POST /game/poker-hand-rank$0.002Developer Utilities
Build a round-robin schedule from participant names
POST /game/round-robin-schedule$0.002Developer Utilities
RPG XP to next level calculator
linear or quadratic curve
POST /game/rpg-xp-to-next-level$0.002Developer Utilities
Validate Sudoku Board Legality
Check Rows, Columns and Boxes
POST /game/sudoku-validate-board$0.002Developer Utilities
Check Tic-Tac-Toe Winner, Draw, or Game in Progress
POST /game/tic-tac-toe-winner-check$0.002Developer Utilities
Build a single-elimination bracket with automatic byes
POST /game/tournament-bracket-build$0.002Developer Utilities
Generate a Word Search Puzzle Grid
Seeded and Reproducible
POST /game/word-search-grid-generate$0.002Developer Utilities
Flower bulb calculator
bulbs needed from bed area and planting density
POST /home/flower-bulbs$0.002Developer Utilities
Bitwise calculator
AND, OR, XOR and shifts on 32-bit integers
POST /math/bitwise$0.002Developer Utilities
Pond volume calculator
gallons from length, width and average depth
POST /home/pond-volume$0.002Developer Utilities
Fence cost estimator
panels, posts, concrete and gate total, free
POST /home/fence-cost$0.002Developer Utilities
Fence gate calculator
posts, hinges and latches from gate count and width
POST /home/fence-gate$0.002Developer Utilities
Fence panel calculator
panels and posts from length and panel width
POST /home/fence-panels$0.002Developer Utilities
Lawn roller fill calculator
water weight from drum diameter and width
POST /home/lawn-roller-fill$0.002Developer Utilities
Lawn topdressing calculator
yd³ sand/compost from area and depth
POST /home/lawn-topdressing$0.002Developer Utilities
Stepping stone calculator
stones from path length and spacing, free
POST /home/stepping-stones$0.002Developer Utilities
Box method calculator
multiply two binomials step by step
POST /math/box-method$0.002