About SDK.bz
Free financial and cryptocurrency calculators that let you model decisions before you make them.
Our Story
We started SDK.bz in 2024 after spending too many evenings rebuilding the same compound-interest spreadsheet from scratch. One of us wanted to know "if I add β©300,000/month for the next 25 years, what is the expected nest egg?", another wanted to compare two crypto-staking opportunities including the lock-up period, and a third wanted to see what happens to a mortgage if the interest rate moves a single percentage point.
Every existing calculator had the same problems: pop-ups, modal email captures, "log in to see the full chart," ads in the middle of the result, and β worst of all β opaque math. Most of them did not document the formula, so you had no way to know whether the answer was right or simply confidently wrong.
So we built calculators we would actually use. Every formula is documented in the guide page. Every input stays in your browser; numbers about your salary, your house, or your portfolio never reach our servers. Every result loads in well under a second and is mobile-first because half of "what's my real take-home pay" questions happen on a phone in a parking lot.
The site is supported by display ads. Ad density is deliberately kept well below the industry average and never placed between an input and its result. If an ad ever made a calculation harder to read, we move or remove it.
Our Mission
SDK.bz exists to give working people a fast, friction-free toolbox for the financial and crypto calculators they actually need every day. We believe everyday utilities should be free, accurate, fast, mobile-friendly, and respect your privacy by default. Whether you are at your desk, on a train, or in a parking lot trying to settle a dinner bill, we want you to find your answer in seconds.
We measure success in three numbers: time-to-answer (target: under 3 seconds from cold load to result), inputs-to-answer (target: as few as possible), and bytes-of-your-data-on-our-servers (target: zero). Everything else is downstream of those numbers.
Long-term, our mission is broader than the current tool catalogue. We want SDK.bz to be the place a friend recommends when you say "is there a calculator for that?" β and have you not feel a flicker of regret when you click the link.
Who We Are
SDK.bz is operated by SDK Co., Ltd., a Korean software company founded in 2024 that builds developer-focused tools and free online utilities. Our team has shipped consumer and developer web products used by millions, and we apply that same attention to UX, accuracy, and speed to every calculator on this site.
Beyond SDK.bz, the same team operates JavaScript.ac (interactive JavaScript learning), SDK.is (developer utilities), SDK.bz (financial and crypto calculators), and SD.gy (everyday calculators). Lessons learned on one site β accessibility patterns, performance budgets, ad-density thresholds β get applied across all of them.
- Company
- SDK Co., Ltd.
- Founded
- 2024
- Focus
- Developer tools, calculators, free utilities
- Business Registration
- 871-81-03242
- E-Commerce Registration
- 2024-κ³ μμΌμ°μ-1820
- Address
- 4F, 127 Namseong-ro, Jeju-si, Jeju Special Self-Governing Province, Republic of Korea
What You'll Find on SDK.bz
SDK.bz ships 10+ financial and crypto calculators today, all free, all running 100% in your browser.
Loan Calculator
Compute monthly payment, total interest, and a full amortisation schedule for any fixed-rate loan. Useful for personal loans, auto loans, and student loans.
Mortgage Calculator
Break down principal, interest, taxes, and insurance (PITI) for a mortgage. Includes a chart of remaining balance over time.
Compound Interest
Model long-term growth with periodic contributions, variable rate, and a yearly summary table. The maths matches the standard FV formula and is documented.
ROI Calculator
Compute simple ROI and annualised ROI from a starting and ending value plus a holding period. Useful for evaluating past investments.
Retirement Planner
Project nest-egg growth and the savings rate required to hit a target portfolio at retirement. Inflation-adjustable.
Currency Converter
Live FX-rate conversion across major currencies. Rate sources are clearly attributed.
Crypto Profit
Model entry/exit-price scenarios with fees and taxes. Supports BTC, ETH, and other major coins.
DCA Simulator
Backtest a dollar-cost-averaging strategy against historical price data and compare against lump-sum buying.
Staking Reward
Compute APY, compounding frequency, and lock-period effects for popular proof-of-stake networks.
Mining Profitability
Estimate revenue from a hashrate, electricity price, and pool fee. Updates with current network difficulty.
Our Principles
Free Forever
No paywalls, no premium tier. Ads keep tools free for everyone.
Privacy-First
All processing happens in your browser. Your data never leaves your device.
Fast by Default
Sub-second load times powered by Cloudflare's global edge network.
Open Access
No login, no signup, no email required. Just open and use.
Mobile-First
Every tool is touch-friendly and works great on phones and tablets.
No Dark Patterns
No fake countdown timers, no roach-motel cookie banners, no manufactured scarcity.
Technology Stack
We chose every piece of the stack to optimise for read speed, write speed, and long-term maintainability with a small team.
Our frontend is built on SvelteKit and TypeScript, styled with Tailwind CSS, and deployed to Cloudflare Pages. We use no traditional backend: pages are statically pre-rendered or generated at request time at the edge, calculator/tool logic runs entirely in the user's browser, and dynamic features that need persistence use the user's own localStorage.
This architecture has practical consequences for you. First, time-to-interactive is measured in tens of milliseconds, not seconds. Second, your inputs never leave your device, so there is no server log to leak. Third, our infrastructure cost is low enough that we can keep SDK.bz free indefinitely without ever introducing a "Pro" tier.
Privacy Promise
All financial and crypto calculators on SDK.bz run client-side in your browser. The text, files, or values you input are never transmitted to our servers. The only data we collect is standard, aggregated analytics (page views, country, device type) and AdSense-related cookies as described in our Privacy Policy. We never sell or share personal data, we never read your inputs, and we never use your activity to train machine-learning models.
If our ad provider changes its consent rules, we will update the consent banner immediately and post a clear changelog entry on the Privacy Policy page. We treat consent as a permanent design choice, not a compliance afterthought.
Contact Us
Have questions, suggestions, or feedback? We'd love to hear from you.
- General questions and feedback: contact@sdk.bz
- Bug reports: please include reproduction steps, browser, and OS.
- Tool suggestions: tell us which calculation or utility you wish existed β real use-cases move our roadmap.
- Partnership and content collaboration: include "Partnership" in your subject line.
- Press and media: same e-mail address, with "Press" in the subject line.
Legal & Operator Information
SDK.bz is operated by SDK Co., Ltd., a Korean corporation registered with the Republic of Korea's Ministry of the Interior and Safety and the Korean Fair Trade Commission.