SandSpan was founded to solve a simple problem: most online unit converters are either inaccurate, bloated with ads, or lack the context needed to understand the results. We built a better way.
To provide free, accurate, and easy-to-understand unit conversion tools for everyday life — from cooking and home improvement to professional HVAC and medical calculations. Every tool on SandSpan is backed by industry-standard formulas and verified against NIST, BIPM, and ASHRAE references.
Our conversion engine uses precise factors (e.g., 1 inch = 25.4mm exactly, 1 lb = 0.45359237 kg). No rounding errors, no approximations. For specialized categories like HVAC (BTU to tons, SEER ratings) and medical dosages (mg/mL, mcg to mg), we follow industry-specific standards.
We believe a calculator should teach, not just compute. That’s why every tool on SandSpan is paired with a detailed guide explaining how the conversion works, when to use it, and what common mistakes to avoid. For example, our concrete calculator doesn’t just give you cubic yards — it explains how to account for waste and over-excavation.
SandSpan requires no sign-up, no tracking cookies beyond essential ads, and no personal data. Everything runs locally in your browser. We keep ads minimal and clearly marked — no pop-ups, no auto-play videos, no intrusive formats.
SandSpan was created by a small team of engineers and content specialists who got tired of inaccurate, confusing conversion tools. Our lead developer has over a decade of experience in web performance and accessibility. Our content team includes former HVAC technicians and medical writers who fact-check every guide.
We’re based in the United States but serve a global audience. Our tools support both metric and imperial units, with special attention to regional differences (e.g., US customary vs. UK imperial gallons).
SandSpan follows WCAG 2.1 AA guidelines. All tools are keyboard-navigable, screen-reader compatible, and maintain a minimum contrast ratio of 4.5:1. We support reduced motion preferences and dark mode for comfortable viewing in any lighting.
Have feedback, found an error, or want to suggest a new unit category? We’d love to hear from you. Reach us at our contact page — we typically respond within 24–48 hours.
Last updated: June 2026