Hit your numbers. Brew beer you're proud of.
Brew Day turns Claude into the brewing buddy who loves the math. Design a recipe to style with every number calculated, get a clock-time brew day plan, sort out your water and mash, nail fermentation and carbonation, and work out what that off-flavour is and how to avoid it next time.
Get Brew Day Brewing Companion for $15 Calculate ABV and priming
- One-time $15
- Instant email delivery
- 14-day refund
- Works on any Claude plan, even free
Recipe: West Coast IPA, 5 gal all-grain
72% efficiency · 60 min boil · fermented at 66°F · US-05
In style on all 5BU:GU 0.98Water: sulphate-forward
- Grain11 lb 2-row (92%), 0.5 lb Crystal 20 (4%), 0.5 lb Carapils (4%)Mash at 150°F for 60 min · dry finishOG 1.063
- HopsColumbus 15% 1 oz @ 60 · Centennial 10% 1 oz @ 10 · Simcoe 2 oz whirlpoolTinseth, boil gravity 1.054 · whirlpool not counted62 IBU
- CalcFG 1.011 at 82% attenuation → ABV 6.8%(1.063 − 1.011) × 131.256.8%
- ColorMorey: about 5.4 SRM, goldenMCU 6.6 → 1.4922 × 6.6^0.68595.4 SRM
Everything between the grain bill and the first pour
Extract, BIAB or all-grain. Beer, cider and mead. US gallons or litres.
Recipe design
Grain bill, hops and yeast to style, with OG, FG, ABV, IBU and color calculated.
Brew day timeline
Clock-time steps from strike water to pitching, with every hop addition.
Water and mash
Strike temperature, volumes, mash pH and salt additions from your water report.
Fermentation
Pitch rates, starters and a temperature schedule that keeps your beer clean.
Bottles and kegs
Priming sugar by style and temperature, keg pressure and line balance.
Off-flavour detective
Butter, green apple, solvent or band-aid: the likely cause, the fix and the prevention.
Ask it like you'd ask the brewer at your club
It looks at your process, not just your recipe.
Most likely: chlorine or chloramine (chlorophenols)
A band-aid or medicinal taste usually comes from chlorine compounds reacting with phenols in the beer. A recipe that worked before points to a change in water or sanitising, not the grain or hops.
Check
- Has your water supplier switched to chloramine? Many do, and it doesn't boil off.
- Are you using a bleach-based sanitiser, or not rinsing a chlorine cleaner?
- Was fermentation warmer than usual? Stressed yeast can add phenolic notes too.
Fix for next time
Add one Campden tablet per 20 gallons of brewing water, crushed and stirred in a few minutes before use. Use a no-rinse acid sanitiser instead of bleach. This batch won't recover, sadly.
Better beer, brewed safely
Brew Day shows its math and keeps you safe around heat, gas and pressure.
- Formulas shownTinseth, Morey and gravity math, so you can check every number.
- Safety built inBurner ventilation, CO2 cylinders, bottle pressure and cleaning chemicals.
- Process before recipesSanitation and temperature control come first, because they matter most.
- Legal homebrewingFor adults, for personal use. It won't help with distilling.
Up and running in two minutes
No app to learn and nothing to install on your computer. It lives inside Claude.
Buy once
Pay $15 by card, Apple Pay or Google Pay. Your download link arrives by email in about a minute.
Add it to Claude
Upload the ZIP in Claude under Customize, then Skills. It takes about 30 seconds. No setup, no accounts.
Just ask
"Design a hazy IPA for my BIAB setup." "What's my strike temperature?" "How much priming sugar for a saison?"
Start with the free Recipe Calculator
A small skill that takes your recipe and works out estimated OG, FG, ABV, IBU and color, shows the working and compares it to your target style.
- Gravity, ABV, IBU and color
- Formulas shown
- Style check with simple fixes
Get Brew Day Brewing Companion
Pay once, use it every brew day. Includes the free Recipe Calculator too.
How to add it
- Claude on the web or desktop: don't unzip it. Open Customize, then Skills, click +, choose Upload a skill and pick the ZIP. It works on any Claude plan, including the free one: just turn on code execution in Settings, Capabilities.
- Claude Code:
unzip brew-day-brewing-companion.zip -d ~/.claude/skills/ - Start a new chat and try: "I brew 5 gallon all-grain batches in a bag. Design me a crisp pale ale and give me a brew day timeline."
Brew Day Brewing Companion
Design, brew, ferment, package and troubleshoot.
$15 one time
- Recipe design to style
- Scaling and extract conversion
- Timed brew day schedule
- Water and mash chemistry
- Yeast and fermentation plans
- Priming sugar and keg pressure
- Off-flavour troubleshooting
- Updates for a year
Secure checkout by Stripe. Taxes calculated at checkout. 14-day refund.
Prefer to buy on Etsy? Get it on Etsy
New to Claude?
Claude is an AI assistant made by Anthropic, like ChatGPT. Brew Day is a skill: a set of expert instructions you add to your own Claude account, so Claude answers like a brewing buddy who loves the math who knows the craft.
- Make a Claude account at claude.ai. Skills work on every plan, including the free one; paid plans give more usage.
- Turn on code execution in Settings, Capabilities (skills need it).
- Try the free Recipe Calculator skill first. If you like it, the full skill is one purchase.
Not ready for Claude? The free ABV and priming sugar calculator on this site works in any browser, no account needed.
Questions
Does it replace brewing software?
It does the same core calculations and shows the formulas, and it adds the reasoning: why a number is off and what to change. Many brewers use it alongside their software.
Extract or all-grain?
Both, plus partial mash and brew in a bag. It can convert recipes between them.
Cider and mead?
Yes. It handles gravity, yeast, nutrients and fermentation for cider and mead too.
Does it include style guidelines?
It knows the usual ranges for common styles and summarises them in its own words. For full descriptions, it points you to the BJCP guidelines.
What do I need to use it?
A Claude account on any plan, including the free one, with code execution turned on (Settings, Capabilities). Free accounts have lower usage limits, so long planning sessions go further on a paid plan. It works in Claude on the web, the desktop app and Claude Code.
What if it doesn't work for me?
Email hello@whatiflabs.ai within 14 days of buying and we'll refund you in full. No forms, no questions.