The fastest way to reach us is email:

hello@nxtolerance.com

What to send

• Corrections — a density that’s off, a bag yield that’s changed, a source we should cite instead. Please include the data sheet or supplier link.
• Calculator bugs — a result that looks wrong. The URL contains your exact inputs (nothing else is recorded), so pasting the link is the best bug report.
• Feature requests — a shape we don’t model, a material preset, a unit you need.
• Anything else — site feedback, the calculators’ math, or how the site is built.

What to expect

ConcreteCalc is a small operation — replies typically take a few days, not hours. For the scope of what the numbers mean (and what they’re not — see the disclaimer), and for where every input comes from, the sources page is the canonical reference.