Tea Brewing Calculator
The right water temperature, steeping time and amount of leaf for each kind of tea — and roughly how much caffeine is in the pot.
Green and white teas scald and turn bitter in boiling water, so they take cooler water and shorter steeps; black and herbal infusions want it boiling.
How the tea brewing calculator works
Green and white teas scald and turn bitter in boiling water, so they take cooler water and shorter steeps; black and herbal infusions want it boiling. Leaf is dosed by water volume, about 2–3 g per 250 ml cup. Caffeine varies with the leaf and the steep; the figures here are typical per cup for a standard steep.
Formula: leaf = cups × ml per cup × g per 100 ml; caffeine ≈ typical mg per cup × cups
Worked examples
| Inputs | Steep for | Note |
|---|---|---|
| Two cups of black tea | 4 min | 4 min at 98 °C, 5 g |
| A pot of green for four | 2.5 min | 2.5 min at 78 °C |
| Strong oolong, one cup | 3.6 min | 3.6 min |
FAQFrequently asked questions
Why not use boiling water for green tea?
Boiling water pulls out tannins and catechins too fast and scalds the leaf, making green tea bitter and astringent. 75–80 °C keeps it sweet and grassy.
How much caffeine is in a cup of tea?
Typically 40–50 mg for black tea, 25–30 for green, 15 for white and about 35 for oolong per 250 ml cup, against about 95 mg for coffee. Longer steeps and more leaf raise it; herbal infusions and rooibos have none.
Can I re-steep the leaves?
Good loose-leaf oolong, green and white teas give two or three infusions — add about 30 seconds each time. Black tea is usually spent after one.
How do I get water to 80 °C without a thermometer?
Let freshly boiled water stand with the kettle lid open: one to two minutes brings it to about 90 °C, three to four minutes to about 80 °C.
Where these figures come from
- US FDA — Safe Minimum Internal Temperatures — the internal temperatures the roasting calculator targets
- NIST SP 811 — Guide for the Use of the International System of Units — the exact weight and volume conversions used throughout
- UK Food Standards Agency — food safety and labelling standards
Last checked: September 2026. Baking ratios follow standard baker's percentage practice; roasting guidance follows published safe internal temperatures.