Heaping Tablespoon to Teaspoons
1 heaping tbsp ≈ 4 to 4.5 tsp
about 40% more than a level tablespoon's exact 3 tsp
A heaping tablespoon is filled above the rim with as much as will stay on the spoon without falling off, rather than swept flat with a knife. That makes it roughly 140% of a level tablespoon: about 4 to 4.5 teaspoons instead of the level 3. It is an approximate measure by its nature. How high the heap sits depends on the ingredient and how you scoop, so unlike a level tablespoon (which is exactly 3 teaspoons), a heaping tablespoon has no single exact teaspoon value. Heaped is simply the British spelling of the same thing; a heaped tablespoon and a heaping tablespoon are identical.
Level, Rounded, Heaping and Scant Tablespoon
Only the level tablespoon has an exact teaspoon equivalent. The others are approximate conventions that vary with the ingredient and how high the spoon is piled.
When Heaping Matters
Coffee and cocoa
Heaping on purpose is normal here. A heaping tablespoon of grounds (about 4 to 4.5 tsp) makes a stronger brew than a level one, and precise volume does not matter.
Flour
Heaping is risky. A heaped tablespoon of flour can hold up to 50% more than a level one, the most common cause of dense, dry bakes. Level flour for baking.
Baking powder and soda
Never heap leaveners. The extra amount changes rise and can leave a metallic taste. Always level, sweeping flat with a knife.
Sugar, spices, loose ingredients
Heaping adds a rough 40% and is fine where a little extra will not break the dish. For anything measured for chemistry, level it.