How many calories in mayonnaise, ketchup and salad dressing?

Condiments are the last thing anyone logs and one of the easiest places to lose several hundred calories a day. Not because the numbers are shocking, but because the serving on the label is a tablespoon and nobody in the history of sandwiches has used a tablespoon.

There are two separate things to get right here. The first is what each sauce costs per gram, which is straightforward. The second is how many grams actually leave the jar, which is where all the error lives.

The quick answer

Nobody uses a tablespoon

This is the actual finding, and it is worth more than the table above. Every nutrition label declares a serving that has almost no relationship to how the product leaves the container.

Spreading a sandwich takes around 25g of mayonnaise, which is 170 kcal. That is more than the two slices of bread underneath it at 190, and it is the single most invisible number in a packed lunch.

The restaurant salad line is worse. A labelled dressing serving is 2 tbsp, or 30g. A kitchen tossing a salad uses a 60g ladle, sometimes two. Caesar dressing at 60g is 300 kcal, which is more than the chicken on top of it.

The salad problem, laid out properly

Take the same salad and change only what goes on it.

The leaves never moved. The chicken never moved. The dish went from 235 to 707 and every one of those 472 calories arrived in a container the diner never sees.

This is the mechanism behind the observation in high-volume, low-calorie foods that a salad is not automatically a light meal. A salad is a delivery system, and what it delivers is decided at the last step.

The false friend shelf

The condiment aisle is one of the places where British and American kitchens diverge most sharply, and several of the words do not travel.

Two of these carry real calorie consequences. Salad cream is not a lighter mayonnaise, despite looking and pouring like one. It is 330 kcal per 100g against 680, so it is genuinely half, but people use it more freely because it behaves like a dressing rather than a spread, and the saving evaporates.

English and American mustard are not the same food and it works in Britain's favour. English mustard is hot enough that a teaspoon is a portion, at about 8 kcal. American yellow mustard is mild enough to squeeze across a whole hot dog, but it is also only 66 kcal per 100g, so even a generous line costs 10. Mustard is the one condiment where neither country can get it wrong.

Light mayonnaise is one of the few light products that works

Most reduced-fat versions of things are a poor trade: the fat comes out, sugar or starch goes in, and the calorie saving is 10%. Mayonnaise is the exception, because mayonnaise is 80% oil and there is a lot of room to remove.

Full fat to light is a 57% cut for a product that does the same job in a sandwich, a coleslaw or a tuna mix. That is a bigger saving than almost any swap available in a supermarket, and it is one of the few where the product genuinely still works.

The honest caveat: extra-light mayonnaise is thin and sharp, and it is the one most likely to make you use double. Doubling extra-light still beats a single spread of full fat by a wide margin, so even the failure mode is fine.

For cold mixes, Greek yogurt with a spoon of mustard is the best trade on the shelf: about 9 kcal per tablespoon instead of 95, and it adds protein rather than removing fat. The full arithmetic on that swap, applied to a tin of tuna, is in the tuna calorie breakdown. It does not survive heat, so keep it out of cooked sauces.

By weight

A 500g jar of mayonnaise is 3,400 kcal, which is more than a day and a half of food. A 500g bottle of ketchup is 510. They sit next to each other in the fridge door and one of them is a seventh of the other.

Sauce on the plates it usually lands on

Two lines deserve attention. In a BLT the mayonnaise costs more than the bacon, at 136 against 130, which is the same point the bacon breakdown arrives at from the other direction. And in a 150g portion of potato salad, the potato is 40 kcal and the mayonnaise is 220. It is a mayonnaise dish with potatoes in it, exactly as the potato post describes for every other potato preparation.

The one place a fatty dressing earns its keep

There is a genuine argument for oil on a salad, and it is worth stating fairly rather than pretending the fat-free bottle wins on every measure.

Carotenoids like beta-carotene and lycopene are fat-soluble, so absorbing them from raw vegetables requires fat in the same meal. A controlled feeding study found substantially higher carotenoid absorption from salads eaten with full-fat dressing than with fat-free dressing. Eating a large raw salad with a fat-free dressing means absorbing a fraction of what is in it.

The practical version is not "pour olive oil freely." It is that a measured teaspoon of olive oil, or a few slices of avocado, does the nutritional job for 40 kcal. The 300 kcal Caesar ladle is not doing anything the teaspoon was not already doing.

Condiment mistakes to avoid

Logging the label serving

The tablespoon on the back of the jar is a fiction for spreads and dressings. Weigh what you use once, then use that number.

Squeezing straight onto food

A squeeze bottle held over a burger delivers whatever your grip decides. A teaspoon delivers 5g. The difference across a week of sandwiches is around 700 kcal.

Treating a dip pot as free

A 30g pot of garlic mayonnaise is 210 kcal. Two of them alongside a chicken meal is 420, which is more than a portion of chips.

Assuming a vinaigrette is the light option

A standard oil-and-vinegar vinaigrette is 450 to 500 kcal per 100g, which is roughly level with ranch. Vinaigrette sounds light because it is thin. The oil is still oil, a point the olive oil breakdown makes in more detail.

Buying "reduced fat" coleslaw and eating more of it

100g of reduced-fat coleslaw is 85 kcal against 150. That is a real saving until the tub gets treated as a side salad rather than a spoonful.

Ignoring sugar in the light versions

Light mayonnaise and fat-free dressings replace some of the oil with sugar and starch. The calories still fall a long way, so the trade is worth making, but the ingredient list is worth reading, and the names sugar hides behind apply here as much as anywhere.

Three ways to spend sauce well

The sandwich that keeps the mayonnaise (343 kcal)

• 2 slices medium wholemeal bread (190 kcal)
• 15g light mayonnaise, spread thin (44 kcal)
• 60g chicken breast, sliced (99 kcal)
• Lettuce and tomato (10 kcal)

Adds up to: 343 kcal with 25g of protein. Using 15g of light mayonnaise instead of the usual 25g of full-fat saves 126 kcal, and a sandwich built this way does not taste like a compromise.

The dressing that costs 40 kcal (277 kcal)

• Large salad with 120g grilled chicken (235 kcal)
• 1 tsp olive oil, 1 tsp red wine vinegar, mustard and pepper, shaken (42 kcal)

Adds up to: 277 kcal. One teaspoon of oil emulsified with vinegar and mustard coats a whole bowl, because the mustard does the emulsifying that a bottle needs three times as much oil to achieve.

The tuna mix that gained protein (189 kcal)

• 1 drained tin of tuna, 112g (130 kcal)
• 60g 0% Greek yogurt (34 kcal)
• 1 tsp Dijon mustard, lemon juice, black pepper (10 kcal)
• Chopped celery and red onion (15 kcal)

Adds up to: 189 kcal with 31g of protein, against 320 for the same tin with two tablespoons of full-fat mayonnaise. Composition figures throughout are from USDA FoodData Central and UK manufacturer declarations.

The verdict

Mayonnaise is 6.8 kcal per gram and ketchup is 1.0. Those two numbers sort the entire fridge door, because everything in it is either an oil emulsion or a vinegar-and-tomato sauce, and there is nothing in between.

The bigger lever is grams, not choice. A tablespoon of mayonnaise is 95 kcal and a spread sandwich is 170. A labelled dressing serving is 30g and a restaurant ladle is 60. In both cases the number people carry in their head is roughly half of what actually left the jar.

Weigh your own spread once, on the bread you actually use, with the jar you actually own. Everything else here is a table you will not need again.

Pairs well with: the olive oil calorie breakdown, tuna by tin, drained and undrained, and high-volume, low-calorie foods.