If there is no measuring spoon, a standard soup spoon or teaspoon can be used instead; but because spoons vary so much from kitchen to kitchen, this only gives a rough estimate and is not recommended for precise recipes.
How much do household spoons vary?
A standard tablespoon holds 15 millilitres and a teaspoon holds 5, but spoons found around the average kitchen can be off by 20-30 percent from that standard. That difference can noticeably change the flavour with small-quantity ingredients like salt and spices, and it can affect how well dough rises with something like baking powder.
Whether the spoon is filled level or heaped also changes the result, so if you are using an ordinary spoon instead of a measuring spoon, levelling it off gives a more consistent outcome.
Could a kitchen scale be an alternative?
For anyone with a precise scale, measuring by weight is far more reliable than measuring by spoon; conversion charts available online show how many grams a tablespoon of a given ingredient weighs. A tablespoon of salt, for example, weighs about 18 grams, while a tablespoon of sugar weighs around 12.5 grams.
What if there is no measuring tool at all?
A standard bottle cap holds roughly the volume of a teaspoon and can give a rough measurement in a pinch, though cap sizes vary too, so this should only be a last resort. A pinch between the fingers should only be used for ingredients like salt and spices, where the amount can be adjusted by taste.
Where does precision matter most?
In cakes and biscuits that rely on baking powder or yeast, precise measurement directly affects the result, so a kitchen scale is the most reliable option when there is no measuring spoon. In soups and stews, where salt and spices can be adjusted by tasting, rough measuring with a household spoon followed by tasting is enough.
Does it matter whether the ingredient is liquid or dry?
Liquid ingredients, like oil or vinegar, fill a spoon right up to the rim and give a fairly clear volume, so measuring liquids with a household spoon is relatively reliable. Dry ingredients are trickier, since how packed or airy they are changes the volume, so lightly filling the spoon with something like flour or cocoa powder and then levelling it off gives a more consistent result.
Points worth keeping in mind
Whichever method you use, if more than one ingredient in a recipe is measured by spoon, using the same spoon consistently, filled to the same level each time, preserves the ratios between ingredients, which matters more than absolute precision. Weighing and noting down a frequently used recipe just once, until you replace your measuring spoons, saves time compared with hunting for one later.