Coffee guides · Evidence-led guide
How much caffeine does an extra espresso shot add?
The short answer
An extra shot is not a universal milligram amount. Compare source-backed extraction totals from the same chain and recipe rather than multiplying a generic espresso figure.
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.
Dated Starbucks UK reference: these records use the Spring 2026 guide. Newer seasonal guides are available; current recipes have not yet been reconciled with this snapshot.
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 espressoUK | 2 shots | 200 mg | Not documented | Manufacturer listedVerified source record · Reviewed 2026-08-23Use this dose · Compare |
| Costa Signature Blend espressoUK | 3 shots | 325 mg | Not documented | Manufacturer listedVerified source record · Reviewed 2026-08-23Use this dose · Compare |
| Costa Signature Blend espressoUK | 4 shots | 400 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 |
| Costa Signature Blend Flat WhiteUK | Small | 241 mg | Not documented | Manufacturer listedVerified source record · Reviewed 2026-08-23Use this dose · Compare |
| Starbucks UK EspressoUK | Single | 44.6 mg | Not documented | Manufacturer listedVerified source record · Reviewed 2026-08-23Use this dose · Compare |
| Starbucks UK EspressoUK | Doppio | 89.1 mg | Not documented | Manufacturer listedVerified source record · Reviewed 2026-08-23Use 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.
Use differences between listed totals
Costa’s dated Signature Blend table lists 100, 200, 325 and 400 mg for one through four espresso shots. The arithmetic increments are therefore 100, 125 and 75 mg. The published series itself shows why a fixed 100 mg multiplier does not reproduce every row.
Extraction names matter
Corto and Cortissimo are recorded separately from standard espresso. A cortado or flat white should use its documented extraction, not whichever espresso row happens to have the same shot count. This is a data-matching issue, not a claim that one style is healthier.
Custom drinks remain estimates
Adding a documented compatible component gives an arithmetic estimate, not a tested recipe. The source table dates remain visible below. If a change lacks usable numeric evidence, the calculator should explain that gap rather than invent a total.
Sources and scope
- Costa Coffee UK store guideGuide applies 30 April–26 August 2026. Source reviewed 2026-08-23.
- Starbucks UK Nutrition & Allergen GuideCore beverage guide version 16 April 2026; Espresso table. Milk substitutions and other customisations can change the finished drink. Source reviewed 2026-08-23.
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.