Coffee Drink
Japanese Iced Coffee: Flash Brew Recipe and Ice Ratio
Japanese iced coffee, also called flash brew, is hot coffee brewed directly onto measured ice. The ice supplies part of the recipe water and chills the coffee as it drips. Unlike cold brew, extraction happens with hot water, so you can make a fresh cold coffee in about five minutes.
Drink Snapshot
- Caffeine
- 96 mg reference237 ml (8 US fl oz) generic brewed-coffee exampleMayo Clinic’s generic serving example; this recipe’s caffeine is not measured.
- Calories
- About 2 kcal referenceGeneric black coffee, 237 g (8.4 oz) USDA servingGeneric brewed-coffee serving estimate. Ice and water add no calories.
Serving, sugar and sources
- Serving
- 1 black flash brew; 20 g coffee, 180 g (6.1 US fl oz) hot water, 120 g (4.2 oz) recipe ice
- Made with
- Hot filter coffee brewed directly onto measured ice
- Sugar
- 0 g added sugar. The base recipe contains only coffee, water and ice. Milk and sweeteners change nutrition.
- Preparation
- About 5 minutes with equipment ready
The two nutrition examples describe generic black-coffee servings. Measure the collected flash brew separately when you need its finished yield. See the full calculation or label comparison.
Key Takeaways
- 1Count hot water and recipe ice together: this brew uses a 1:15 coffee-to-total-water ratio.
- 2The 300 g (10.1 US fl oz after melting) water budget is not finished drink yield: grounds retain water, and extra serving ice is separate.
- 3Start with the timed pour below, then adjust grind by taste.
On This Page10 Sections
Japanese Iced Coffee Ratio
Use a 1:15 coffee-to-total-water ratio, counting both hot water and recipe ice. Hot water extracts the grounds; melting ice completes the water budget shown below. Comparing only the hot-water portion would describe a different ratio, 1:9.
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| What to weigh | Amount | What it means |
|---|---|---|
| Ground coffee | 20 g | Dry dose |
| Hot brew water | 180 g (6.1 US fl oz) | All pours combined, including the bloom |
| Recipe ice | 120 g (4.2 oz) | Ice in the server before brewing |
| Total recipe water | 300 g (10.1 US fl oz after melting) | Hot water plus recipe ice, not finished yield |
| Optional serving ice | 40–60 g (1.4–2.1 oz) | Added after brewing; outside the initial water budget |
Why Published Flash-Brew Ratios Differ
Our calculation of two published recipes puts their ice and hot water on the same basis. Kurasu Kyoto specifies 16 g coffee, 150 g water and 70 g ice; Counter Culture specifies 30 g coffee, 335 g water and 165 g ice.
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| Recipe | Total water including ice | Coffee-to-total-water ratio | Ice share of total water |
|---|---|---|---|
| Kurasu Kyoto | 220 g | 1:13.75 | About 32% |
| Counter Culture | 500 g | About 1:16.7 | 33% |
| This home recipe | 300 g | 1:15 | 40% |
The table compares published inputs; brewers, grind and pour schedules differ. This recipe uses a larger ice share and less hot water per gram of coffee, which makes careful extraction useful. To adapt another recipe's hot-water and ice split, see the Japanese iced coffee method guide.
How to Make Japanese Iced Coffee
Start medium-fine, close to your usual hot pour-over grind. All times below run from the first pour; all pour weights are cumulative hot water, after taring.
Recipe
Japanese iced coffee
- Makes:
- 1 serving (finished yield varies)
- Time:
- About 5 minutes with equipment ready
Ingredients
- 20 g medium-fine ground coffee
- 180 g (6.1 US fl oz) filtered water heated to 94°C (201°F)
- 120 g (4.2 oz) ice for the brewing server
- 40–60 g (1.4–2.1 oz) fresh ice for serving, optional
Equipment
- V60 02 or similar dripper and paper filter
- server, scale and timer
- kettle
- 350–400 ml (11.8–13.5 US fl oz) serving glass
Method
- Prepare. Fit a paper filter in a V60 02 or similar dripper. Rinse with separate hot water; discard the rinse.
- Add ice. Weigh 120 g (4.2 oz) ice into the server. Place the dripper on top and the whole setup on a scale.
- Bloom. Add 20 g coffee and tare. Start the timer, pour 40 g (1.4 US fl oz) water at 94°C (201°F), and wait until 0:40–0:45.
- Pour. Reach 110 g (3.7 US fl oz) cumulative hot water by about 1:15, then finish the pour at 180 g (6.1 US fl oz) by about 2:00.
- Drain. Let the coffee drain. Total drawdown around 2:45–3:30 is a diagnostic range, not a requirement; judge the cooled coffee.
- Serve. Remove the dripper and swirl until the recipe ice melts. Serve promptly, with 40–60 g (1.4–2.1 oz) fresh ice if desired.
Recipe notes
Pour weights are cumulative hot water after taring the full setup. Rinse water is separate.
180 g (6.1 US fl oz) water + 120 g (4.2 oz) recipe ice = 300 g (10.1 US fl oz after melting) water input, not finished yield. Extra serving ice is optional.
Adjust the grind for your brewer and beans after tasting the cooled coffee.
See the pour-over brewing method for filter setup and pouring technique; use this recipe’s hot-water and ice amounts.
The grounds retain some water, so brewing-water input is not finished drink yield. Weigh the finished coffee if you need an exact beverage yield. A 350–400 ml (11.8–13.5 US fl oz) glass gives space for this serving and optional fresh ice; glass capacity is not the recipe yield.
Japanese Iced Coffee Calories and Caffeine
Black Japanese iced coffee has very few calories and no added sugar in this recipe. As a reference, a 237 g (8.4 oz) cup of generic brewed black coffee has about 2 kcal. Milk, cream and syrup need to be counted separately.
Caffeine in this 20 g recipe is unmeasured. Mayo Clinic’s 96 mg per 237 ml (8 US fl oz) brewed coffee is a separate reference; bean species, dose and extraction determine the actual amount, not glass size or water input.
Serving assumptions and nutrition sources
USDA's generic brewed-coffee record gives 1 kcal per 100 g. Its 237 g household cup therefore gives 2.37 kcal, rounded to about 2. This mass-based reference is separate from Mayo Clinic's 237 ml caffeine example.
Adding more ordinary ice dilutes the coffee as it melts; it does not remove caffeine already extracted. Nor is flash brew always higher or lower in caffeine than cold brew: the concentrate, dilution and amount served all matter.
Why Hot Brew Over Ice Works
This method separates two jobs: hot water extracts the coffee, then ice cools it in the server. UCC’s Japanese brewing guidance distinguishes rapid chilling after hot extraction from cool-water extraction.
Japanese iced coffee suits my habit of deciding I want a cold cup only when I'm ready to brew. I can make it then, without having planned an overnight steep the day before.
Flash brew can suit readers who want to explore a coffee’s fruit or floral character in a cold drink. Those notes depend on the beans and recipe. For a broader choice of methods, see iced coffee.
Adjusting Japanese Iced Coffee Grind and Pours
Taste after swirling and chilling. A timer can reveal a change in flow, but it cannot diagnose flavor on its own.
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| What you notice | First check | One useful adjustment |
|---|---|---|
| Sour and thin, with fast flow | Correct dose and complete 180 g (6.1 US fl oz) hot-water pour | Grind one small step finer |
| Bitter or drying, with slow flow | Filter seating and heavy agitation | Try a slightly coarser grind or gentler pour |
| Weak after adding serving ice | Extra ice or water beyond the recipe | Taste before adding extra ice; keep additions measured |
| Warm after the recipe ice melts | Warm glass or equipment and actual ice weight | Pre-chill the serving glass and use fresh serving ice |
| Inconsistent from cup to cup | Pour totals, grind and timer start | Keep inputs fixed and change one variable at a time |
If you prefer a lower ice share, move some water from ice to the hot pour while keeping the total at 300 g (10.1 US fl oz after melting). That changes extraction and chilling together, so treat it as a new recipe adjustment rather than an equivalent swap.
Japanese Iced Coffee, Flash Brew and Mizudashi
Flash brew and iced pour-over commonly describe this hot-over-ice method. Japanese guidance also describes rapid-chill iced coffee, 急冷式アイスコーヒー. Mizudashi refers to cool-water extraction and belongs with cold brew.
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| Method | How it extracts | When it becomes cold |
|---|---|---|
| Japanese iced coffee / flash brew | Hot water through coffee onto measured ice | During brewing |
| Chilled brewed coffee | Coffee brewed hot, then cooled | Before serving over ice |
| Cold brew / mizudashi | Coffee in cool water for hours | It is extracted cool |
The sources reviewed establish the method’s use, not one inventor or a precise invention date.
Best Coffee for Flash Brew
Start with a coffee you already enjoy as hot filter coffee. A roast described with citrus or floral notes is a reasonable choice if that is the style you want; chocolate or nut notes may suit a rounder preference. Use the label as a buying cue, then judge the cooled cup.
For a larger batch, doubling to 40 g coffee, 360 g (12.2 US fl oz) hot water and 240 g (8.5 oz) recipe ice preserves the input ratio. Use a brewer and server that can hold it; a larger bed may need a different grind and pour schedule, so do not simply double every time target.
Questions About Japanese Iced Coffee
Is Japanese Iced Coffee Watered Down?
Melting ice dilutes the hot extract by design. When it is counted from the start, that dilution is part of the recipe. Unmeasured extra water or serving ice can make the final drink weaker than intended.
Can I Use a Different Pour-Over Brewer?
Yes. A flat-bottom brewer or another paper-filter cone can work. Keep the input ratio for the first attempt, then adjust the grind and pours for its flow. The V60 timing here is a starting point, not a specification for every brewer.
Why Did All the Ice Melt?
The recipe ice is intended to melt into the drink. Swirl after removing the dripper. Fresh serving ice is optional and separate; it helps keep the drink cold but adds further dilution over time.
Is Flash Brew Stronger Than Cold Brew?
Neither name fixes strength or caffeine. Compare each recipe’s coffee dose, water and final dilution. A ready-to-drink cold brew and a concentrate are not equivalent comparisons.
Editor's Take
Research Notes and Sources
Recipe methods, terminology and reference nutrition were reviewed on October 1, 2026. Ratios and ice shares in the comparison are our calculations from the linked recipes.
5 references
External links open in a new tab
Method and terminology
- Kurasu KyotoIced pour-over recipePublished 16 g coffee, 150 g water and 70 g ice recipe; input-ratio comparison.(opens in a new tab)
- Counter Culture CoffeeFlash-brew guidePublished 30 g coffee, 335 g hot water and 165 g ice recipe.(opens in a new tab)
- UCCRapid-chill and cool-water methodsJapanese guidance distinguishing hot extraction and rapid chilling from cool-water brewing.(opens in a new tab)