About
BrewToolbox exists because the arithmetic of brewing is settled and almost nobody presents it that way. The formulas have been published for decades. What's been missing is a set of tools that apply them to your brewhouse, show their working, and tell you the truth even when the truth is "you don't need to buy anything."
Ask the internet how much yeast to pitch and you'll get three kinds of unhelpful answer. The packet says "one sachet per 5 gallons," which is about half the rate the textbooks give and doesn't know your gravity. Forum answers come without units — "just throw in a pound of DME" — with no idea of your volume. And the genuinely good math is locked inside recipe software you have to sign up for.
There's a fourth, particular to brewing: calculators that quietly pick one formula and hide the choice. Two sites will tell you the same beer is 36 IBU and 45 IBU, and neither will mention that one used Tinseth and the other Rager, or that the gap flips direction depending on when the hops went in. That's not a rounding difference. It's the kind of thing a tool should show you rather than resolve on your behalf.
Meanwhile the actual science is public and has been for years — extract potentials, infusion equations, hop utilization curves, pitching rates. None of it is secret. It just needs implementing with some care, attaching to the one thing that makes it personal — your equipment — and explaining without an upsell attached.
I'm Brian Hamilton, and I build every calculator on this site. I'm not a professional brewer, and I'm not going to pretend to be one. I build calculation tools for a living — thirty years of software development, an internet engineering degree, and a stretch building mathematical models for sports prediction companies. This site is that work pointed at wort.
I think that's the right qualification for this particular job, and here's the honest reasoning: most of brewing is a math problem wearing a rubber apron. The equations are settled and published. What goes wrong in practice isn't the science — it's a volume that was estimated rather than measured, a hydrometer read warm, an efficiency number borrowed from someone else's system, and advice shaped by what the person giving it happens to sell. Those are engineering and integrity problems, and they're the ones I can actually fix.
Where genuine domain expertise is required, I lean on the people who have it and say so by name — see the sources below. And where I'm uncertain, the site says it's uncertain rather than rounding up to confidence: the IBU page shows both formulas disagreeing, the refractometer page calls its corrections regressions, and the pitch-rate page prints the honest three-fold spread in how many cells a dry sachet actually contains.
BrewToolbox is one of a family of Toolbox calculator sites I build — pools, brewing, cycling, RVs, soap making and more — alongside the puzzle games and apps I've worked on for years. My author profile has the longer version.
BrewToolbox is published by Hamilton Digital Media Limited, which publishes puzzle games, apps and books, and builds practical online tools and calculators. It's a small UK company, and it's the legal entity that answers for this site — the one named in the terms and privacy policy.
Not "trust us" — here's the mechanism, and you can check every part of it yourself.
Every number comes from a published formula — Tinseth, Rager, Palmer's infusion equations, the ASBC methods — implemented from the source and cited on the page, rather than copied from another site's table where an error would propagate silently.
All 34 calculators call the same calculation modules. Two tools on this site physically cannot give you different answers for the same wort, because there is only one implementation of each formula.
The engine is covered by a test suite that runs on every change, pinned to published reference values — Palmer's worked examples, Tinseth's own numbers, the ASBC tables. If a change would alter a known-good result, the build fails before it reaches you.
Every result has a "show the math" panel with the actual arithmetic, in your units. You should never have to take a number on trust — and if the reasoning looks wrong, you can see exactly where.
The brewing science here isn't ours and we don't claim it. Hop utilization comes from Glenn Tinseth's published curves and Jackie Rager's earlier ones — both shown, because recipes were written in both. Mash and infusion math follows John Palmer's How to Brew; extract potentials and recipe formulation lean on Ray Daniels' Designing Great Beers. Gravity, real extract and calorie methods are the American Society of Brewing Chemists'. Pitching rates follow Chris White and Jamil Zainasheff's Yeast. Refractometer corrections use Sean Terrill's fits and Novotny's later refit. Malt and yeast figures come from maltsters' and labs' own data sheets.
Our contribution is the implementation, the testing, the equipment profile that makes the numbers yours rather than generic, and the writing — plus a stubborn insistence on showing the arithmetic so you're never asked to take a number on faith.
A site whose entire promise is "the numbers are right" has to mean it, which means being easy to correct. If you find a mistake — in a calculation, a formula, a recommendation, or a fact in an article — [email protected] goes straight to a person. We'll fix it quickly and note on the page what changed and when. No defensiveness, no quiet edits.
That's not politeness. Brewing has edge cases, hop lots vary, malt specs differ by maltster, and half the published formulas are fits rather than physics. A correction channel that people actually use is the cheapest quality control there is.
Some links to equipment will earn a commission at no cost to you. That's the whole model — no ads that follow you around, no paid reviews, no sponsored placements, and nothing gated behind a signup. The rules are written down in the affiliate disclosure, and the important one is this: the math picks the recommendation, and we say so when the cheap option is the right one. Plenty of the best answers in brewing — a $10 hydrometer read correctly instead of a $60 refractometer read wrong, a bag in a pot instead of a three-vessel rig, $30 of temperature control before $900 of shiny kettle — earn us almost nothing. We publish them anyway, because a site that recommends whatever pays best gets read once.
As it happens, there are no affiliate links on the site at all yet. The calculators came first.
BrewToolbox is new. 34 calculators are live: the Gravity & ABV, Mash & Water, Hops, Yeast & Fermentation, Packaging, Mead, Cider & Cost and Recipe & Planning groups are complete, and the yeast tools are under way. The Brew Day view that ties them together — plan, timers, and a log that works out your real efficiency — is being built now, with the guides that explain the why behind each number following close behind.
Your equipment is remembered in your own browser so you don't retype it every visit — and it never reaches us, which is the sort of thing that's easy to promise and easy to verify: the privacy policy lists exactly what's stored on your device right now, and there's a button there that deletes the lot.