Jacket potato with tuna mayo: how much it costs to make, per serve
A large baked potato (about 375 g) split and buttered, filled with tuna mayonnaise with sweetcorn and served with a small salad of iceberg and cucumber. Costed from JJ Foodservice wholesale prices dated 9 October 2026.
The menu price is the one ChefSums uses for this dish on its sample café menu, a realistic UK menu price. The lowest price is the one that just reaches 68% GP, the UK food GP benchmark (UKHospitality × Christie & Co, 2022: 65.9–69% food GP across every segment). It covers the ingredients at a normal margin, not staff, rent or energy, and most cafés, pubs and takeaways charge more for simple dishes. Check what places near you charge. GP is worked out on the ex-VAT price.
Open in ChefSums — edit, cost, scale →
Ingredients and cost, one serve
| Ingredient | Pack price | Pack size | Used | Cost |
|---|---|---|---|---|
| Baking potatoes (about 40 to a case) | £12.99 | 40 each | 1 each | £0.32 |
| Unsalted butter | £30.49 | 5000 g | 10 g | £0.06 |
| Tuna chunks in brine (130 g can weight, about 95 g drained) | £7.49 | 1700 g | 130 g | £0.57 |
| Mayonnaise | £15.49 | 5000 ml | 35 ml | £0.11 |
| Sweetcorn | £5.99 | 2230 g | 30 g | £0.08 |
| Iceberg lettuce | £9.99 | 10 each | 0.1 each | £0.10 |
| Cucumbers | £7.99 | 14 each | 0.1 each | £0.06 |
| Table salt | £10.99 | 6000 g | 1 g | £0.00 |
| Total | £1.31 | |||
Cost per line is pack price × (amount used ÷ pack size), the same sum the tool runs. Change one pack price and every line that uses it moves.
What it really costs: waste and staff time
| Ingredients | £1.31 |
| Waste allowance, 5% (trim, ends, the odd one binned) | £0.07 |
| Staff time: 4 min hands-on per serve at £12.71/hr + 25% on-cost | £1.06 |
| Food, waste and staff per serve | £2.44 |
At the sample café menu price (£7.08 ex VAT) that is 34% of the price, before rent, energy and everything else. Many UK sites aim to keep food plus staff (prime cost) at or under 60–65% of sales. The staff line counts hands-on prep only, not unattended cooking, and uses the April 2026 National Living Wage; put your own rate, minutes and waste in the calculator's real cost section or the prime cost calculator. Every dish side by side: the UK dish cost index.
Method
- Rub the potato with a little salt and bake at 200 °C for 60-75 minutes, until the skin is crisp and a knife goes in with no resistance.
- Drain the tuna well, then mix with the mayonnaise and sweetcorn; season.
- Split the potato, butter it, pile in the filling and add the side salad.
Costing notes
The tuna is costed on can weight because that is what you pay for: a 1.7 kg catering tin drains to roughly 1.2 kg of fish, so 130 g from the can gives about 95 g of tuna on the potato. Pre-made tuna mayo filling (about £8.49 for 1 kg at JJ the same day) costs more per portion but saves prep time.
A case of about 40 baking potatoes means potatoes of roughly 375 g; if your case comes in at 50, each potato is smaller and cheaper, and the portion looks it.
Where the prices came from
JJ Foodservice collection prices as shown on its public search pages on 9 October 2026 (delivery runs about £1-2 a case higher). A few lines JJ did not list in that day's searches reuse the dated prices already on our other starter recipes (7 September 2026, JJ Foodservice or Tesco retail, marked on each line). JJ does not label VAT on most lines: raw food is zero-rated in the UK, while soft drinks, alcohol, confectionery and some ingredients carry standard-rate VAT. Your supplier's price is the one that matters: open the recipe and type it in.
- Baking potatoes (about 40 to a case): Baking Potatoes Approx 40 1x15kg, 40 each, £12.99 collection — JJ Foodservice, accessed 2026-10-09
- Unsalted butter: Lakeland Unsalted Butter 20x250g (DAI186), 5 kg, £30.49 collection — JJ Foodservice, accessed 2026-10-09
- Tuna chunks in brine (130 g can weight, about 95 g drained): JJ Tuna Chunks in Brine Single Tin 1x1.7kg, 1.7 kg, £7.49 collection — JJ Foodservice, accessed 2026-10-09
- Mayonnaise: Heinz Professional Mayonnaise 1x5L, 5 L, £15.49 collection — JJ Foodservice, accessed 2026-10-09
- Sweetcorn: JJ Sweetcorn 1x2230g, 2.23 kg, £5.99 collection — JJ Foodservice, accessed 2026-10-09
- Iceberg lettuce: Iceberg Lettuce 1x10-12, costed at 10 a case, 10 each, £9.99 collection — JJ Foodservice, accessed 2026-10-09
- Cucumbers: Cucumbers Class I 1x14-16, costed at 14, 14 each, £7.99 collection — JJ Foodservice, accessed 2026-10-09
- Table salt: DP Table Salt Tub 1x6kg (SPI277), 6 kg, £10.99 collection — JJ Foodservice, accessed 2026-10-09
More costed dishes: café and breakfast
- Cheese and ham toastie — £1.18 a serve
- Egg mayo sandwich — £0.57 a serve
- Beans on toast — £0.60 a serve
- Fish finger bap — £1.23 a serve