Coffee Extraction Ratio & 4:6 Method Timer
A hand-drip coffee ratio calculator that calculates total water amount from bean weight and ratio, guides the pouring schedule for the 4:6 method (Kasuya-style) with a step timer. Also supports contactless gesture control by holding your hand over the camera.
How to Use
- Enter bean weight in "4:6 Method" mode (default 20g)
- Select a ratio (default 1:15 = 300g total water. 1:15–1:18 or custom also available)
- Choose taste (acidic to sweet) for the first 40% (2 pours), and strength (weak to strong) for the final 60% (number of pours)
- Review the displayed pouring schedule (amount per pour, cumulative, timing) and tap "Start Timer"
- The timer notifies you of each pour timing at 45-second intervals with beeps and vibration
- If your hands are wet and you don't want to touch the screen, start "Gesture Control," hold your open hand for 0.6 seconds to start/stop the timer, and swipe left/right to go to the next/previous step
- Use "Ratio Calculation" mode to work backward from your available water amount to determine the required bean amount
Use Cases
- When you want to quickly know the total water amount and each pour amount based on bean weight for your daily hand-drip coffee
- When you want to brew using the 4:6 method (Kasuya-style) while adjusting taste and strength
- When you want a timer to guide the timing of each pour
- When you're holding a kettle or have wet hands and want to control the timer with gestures without touching the screen
- When you want to work backward from your available water amount to determine the required bean amount
Frequently Asked Questions
What is the 4:6 Method? ▼
It is a hand-drip brewing method devised by Tetsu Kasuya, world barista champion. Water is split into the first 40% and final 60%; taste (acidic to sweet) is adjusted over 2 pours in the first phase, and strength is adjusted by the number of pours in the final phase. This tool auto-calculates pour amounts, cumulative amounts, and timing from bean amount and ratio.
How do taste and strength change? ▼
Increasing the first pour of the first 40% yields more acidity; decreasing it yields more sweetness. More pours in the final 60% yield stronger coffee, fewer pours yield lighter coffee (light = 1 pour, standard = 2 pours, strong = 3 pours). The default "strong" uses 5 pours of 60/60/60/60/60g each, reproducing one of Kasuya's signature recipes.
What are the recommended water temperature and grind size? ▼
For the 4:6 Method, water temperature of 90–93°C and medium-coarse to coarse grind are typical (higher temperatures work better with light roasts, lower temperatures with dark roasts). This is also shown in the guide below the tool.
Is camera video from gesture control sent externally? ▼
No. Hand recognition is performed in-browser (WASM + WebGL) using MediaPipe GestureRecognizer (Apache-2.0), and neither video nor recognition results are sent outside your device. The recognition model is only loaded when you tap "Start Gesture Control" (first time only, ~20MB), and is not loaded at all during normal use.
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