How this calculator works
Tea is brewed by steeping leaf in hot water long enough for the soluble compounds to come out. More leaf, hotter water and a longer steep all extract more, but they do not extract the same things: the brisk, astringent compounds come out later than the aroma and the caffeine, so an over steeped green tea turns bitter while a black tea needs the heat and time to open. The standard preparation in ISO 3103 uses 2 g of leaf per 100 mL of boiling water for six minutes, which is a tasting method rather than a drinking recipe; everyday brewing uses less time and, for green and white teas, cooler water. This page uses 2 g per 100 mL as the base, then moves the temperature and time by tea type, and scales the leaf for strength. The leaf amount is far more precise by weight than by spoon because leaf size and shape change the volume a lot.
Formula
leaf (g) = grams per 100 mL x water volume (mL) / 100 x strength factor. Water volume of one cup is 240 mL. The strength factors are 0.75 for light, 1 for standard and 1.25 for strong. Temperatures are 95 C for black and pu erh, 90 C for oolong, 80 C for green and white, and 100 C for herbal infusions. Steep times are 4 minutes for black and pu erh, 2.5 for green and white, 3.5 for oolong and 6 for herbal.
Worked example
A 240 mL cup of black tea at standard strength needs 2 x 240 / 100 = 4.8 g of leaf, steeped at 95 C for 4 minutes. The same cup at light strength needs 4.8 x 0.75 = 3.6 g, and at strong 4.8 x 1.25 = 6.0 g. A one litre pot of green tea at standard strength needs 2 x 1000 / 100 = 20 g of leaf, brewed at 80 C for 2.5 minutes. The pot makes 1000 / 240 = 4.2 cups.
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Frequently asked questions
Should I use boiling water for every tea?
No. Black tea, pu erh and herbal infusions take water at or near the boil, but green and white teas are better at 75 to 85 C. Boiling water scalds the leaf and brings out bitterness before the sweetness and aroma have had time to develop.
How much tea leaf is in a tea bag?
A typical tea bag holds about 2 g of tea, close to the amount for one 240 mL cup at standard strength. The bag restricts the leaf, so the same weight in loose leaf usually tastes fuller. If you are using bags, count them rather than weighing the leaf.
Why does the calculator scale leaf but not steep time for strength?
More leaf with the same steep raises the concentration without over extracting, while a longer steep pulls out the bitter compounds. For a stronger cup, add leaf first. If you prefer a longer steep, use a light leaf amount and check the taste before the time in the table.
Does tea have caffeine?
Yes, unless it is an herbal infusion made without tea leaf. Black tea has about 47 mg per 240 mL and green tea about 28 mg, less than a cup of brewed coffee. The caffeine counts towards the Health Canada daily limits, so it belongs in the same tally as coffee and cola.