Research methods · Evidence-led guide
Why coffee caffeine figures disagree: sizes, recipes and sources
The short answer
Two different caffeine figures are not necessarily a contradiction. They may describe different portions, markets, preparations, source dates or evidence methods.
Dated Costa reference: the recorded guide covers 30 April–26 August 2026. A newer recipe has not been verified; confirm the current menu before relying on an exact amount.
| Check | Question to resolve |
|---|---|
| Market | Do both figures describe the same country’s recipe? |
| Serving | Are these per shot, per cup, per 100 ml or per package? |
| Preparation | Is the extraction, blend and recipe the same? |
| Version | Do the source dates and menu periods match? |
| Evidence | Is each figure listed, calculated, reported or approximate? |
If one field cannot be matched, retain the uncertainty rather than choosing the more convenient number.
Inspect the documented servings
These values come from the linked catalogue records. A source-backed record is not a measurement of your drink or a guarantee of a current recipe.
| Drink / market | Serving | Caffeine | Per 100 ml | Evidence / action |
|---|---|---|---|---|
| Costa Signature Blend espressoUK | 1 shot | 100 mg | Not documented | Manufacturer listedVerified source record · Reviewed 2026-08-23Use this dose · Compare |
| Costa Signature Blend CortadoUK | Standard | 141 mg | Not documented | Manufacturer listedVerified source record · Reviewed 2026-08-23Use this dose · Compare |
| EspressoGeneral reference | 1 fl oz / 30 ml | 63 mg | 210 mg (calculated) | Authoritative referenceVerified source record · Reviewed 2026-08-21Use this dose · Compare |
Bars use the selected measure; numbers remain visible in both units. No bar is drawn for an undocumented concentration. Per 100 ml = serving caffeine × 100 ÷ documented volume.
Start with the denominator
A concentrated small serving can contain less total caffeine than a diluted large serving. Convert only when a usable volume is documented. Do not treat grams of finished drink as millilitres without evidence.
Do not erase extraction differences
The dated Costa guide distinguishes standard espresso and Corto. The general espresso reference is yet another kind of evidence: it is not Costa’s recipe. Combining these numbers under a single “shot” label would hide the main reason they differ.
Review dates are not recipe dates
An editor can inspect an old document today without making its recipe current. CaffCalc preserves both the source version and review date. A later article update does not mean every underlying source has changed or been reverified.
Prefer correction over false precision
A defensible correction names the source, serving, country and value basis. Missing fields should stay missing until supported. CaffCalc does not claim independent laboratory testing or turn an approximate supplier figure into an exact first-party measurement.
Sources and scope
- Costa Coffee UK store guideGuide applies 30 April–26 August 2026. Source reviewed 2026-08-23.
- USDA FoodData CentralRepresentative reference value; café recipes and extraction vary. Source reviewed 2026-08-21.
Educational information, not medical advice. Published, calculated and approximate values have different limits. Check the current product label or recipe when an exact amount matters.