Help Toolz — Free Browser Tools

All 18 tools

• World Clock — See what time it is in cities you care about.

  Add the places where you work, travel, or have family. Click any hour to highlight it across every row. Drag to mark a time range.

• Timezone Overlap Finder — Find meeting times that work for everyone.

  Add the people on your team and the hours they actually work. Get a heatmap of the next two weeks with the slots where everyone is available.

• Cron Job Editor — Plain English to cron expression.

  Type a schedule the way you would say it out loud. Get back a working cron line and a calendar that shows when it will run.

• Palette Checker — WCAG contrast and colorblindness for the whole palette.

  Drop in your brand colors. See every foreground and background pair tested against WCAG AA and AAA. Switch to deuteranopia, protanopia, or tritanopia and watch the matrix update.

• Citation Converter — Reformat a bibliography between citation styles.

  Paste BibTeX, RIS, or plain text. Get APA, MLA, Chicago, IEEE, Vancouver, or Japanese JST output. Handles CJK author names and non-Latin scripts that other tools choke on.

• Unit Converter — Engineering unit converter for the edge cases.

  Not feet to meters. Torque conventions across automotive and aerospace, cP vs Pa·s vs SSU viscosity, radiation dose, semiconductor wafer specs, and the three different definitions of horsepower.

• Contract Rate Calculator — Salary to hourly contractor rate, with the math nobody else does.

  Most "salary to hourly" tools just divide by 2080. This one accounts for what your employer actually pays for you (benefits, employer FICA) and what you have to cover yourself as a contractor (self-employment tax, healthcare, retirement, business overhead, bench time).

• Heat Pump Sizing Calculator — Size a heat pump and estimate IRA tax credits. US homes.

  Climate-zone-aware sizing combined with installed-cost estimates and the actual federal incentive math: Sections 25C and 25D tax credits plus the income-tested HEEHRA rebate up to $8,000. Plus annual operating cost compared to your current furnace.

• Carbon Offset Cost Calculator — Compare offset types by quality, permanence, and price.

  Most "carbon offset calculators" are sales pages from offset providers. This one is neutral. Quality grades reflect academic consensus and the 2023–2024 investigations that exposed widespread over-crediting in REDD+ and cookstove projects.

• AWS Cost Calculator — Estimate AWS bills by workload pattern, not service-by-service.

  AWS's own calculator asks you to configure 50 things. This one asks for 3-5. Pick what you are building (static site, serverless API, web app, container app, ML inference, ML training, backup), fill in realistic numbers, get a service-by-service breakdown.

• FDA 510(k) Predicate Finder — Search the FDA cleared-device database and compare predicates.

  Searches the FDA's public 510(k) database (via openFDA) for cleared medical devices. Filter by device name, applicant, product code, K-number, or decision date. Pick up to four records and see them side by side, with direct links to the official FDA record and 510(k) summary PDF.

• Regex Visualizer — See a regex as a railroad diagram, explained in plain English.

  regex101 is dense and intimidating. Debuggex is half-abandoned. This one parses your pattern, draws it as a railroad diagram (boxes, branches, loops), and explains every piece in plain English next to it. Live tester with match highlighting and capture groups.

• Startup Cost Calculator — How much it actually costs to start a small business by state and industry.

  Pick your state, business type, and structure. Get an itemized list of every check you'll write — state filing fees, federal forms, industry licenses, insurance minimums, equipment baselines, working capital. Honest ranges. The tool that LegalZoom won't build because they make money selling you their service.

• Patent Filing Cost Estimator — Real numbers for a US patent over 20 years — not "it depends, contact us".

  Pick patent type, entity size, complexity, and add-ons. Get an itemized 20-year timeline showing every USPTO fee, attorney bill, and maintenance payment. Reveals how the total breaks across filing day, office actions, issue, and the three maintenance fee deadlines that decide what survives.

• Cap Rate Sanity Check — Is this a good cap rate? Compare against actual market comps and 5-year history.

  Pick asset class, market tier, and property class. Enter the cap rate (or NOI + price). See whether the deal is in line, compressed, or wide vs current Q4 2024 transaction data — plus where the segment has been across the cycle. The opposite of a "what is cap rate" article.

• E-commerce Break-Even Calculator — Real contribution margin and break-even units. Models the fees blog calculators skip.

  Pick your channel (Shopify, Amazon, Etsy, eBay, Walmart, TikTok Shop, custom). Enter price, COGS, shipping, returns, and CAC. Get per-order contribution math, monthly break-even units, and profit at sample volumes — including non-refunded fees on returns and restocking write-offs.

• Tipping Guide by Country — How much to tip in 80+ countries — and the cultural context the listicles skip.

  Pick a country, see the actual tipping norms for restaurants, bars, cafes, taxis, hotel housekeeping, hotel porters, spas, and tour guides. Plus the cultural context that matters: where tipping is rude (Japan, Iceland), where USD cash is gold (Argentina, Cuba, Egypt), and where service charge replaces the need to tip (France, Singapore, Brazil).

• Marketplace Fee Calculator — Etsy, Amazon, eBay, Mercari, Poshmark — what you actually take home.

  Real fee math for the five biggest seller marketplaces, no ad-stuffed listicle. Etsy with country-specific payment processing + offsite ads + regulatory fees. Amazon with category-specific referral % + FBA tier + closing fees. eBay with FVF + per-order + promoted listings + international surcharge. Plus side-by-side comparison of all five for the same item.

Why these tools

Every tool here exists because the existing options are slow, paid, full of ads, or hidden behind a sign-up screen. These are not. You open the page and the tool works.

Nothing leaves your browser. Your zones, schedules, and selections live in local storage on your own device. The pages have no analytics on your inputs and no fingerprinting.

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