How many grams is 1 tablespoon of chopped celery?

1 tablespoon of chopped celery weighs

7.5g

That's 0.3oz. An Australian 20ml tablespoon holds 10g.

A level US or UK tablespoon (15ml).

Other amounts of chopped celery

1 cup: 101g
Half a cup: 51g
A quarter cup: 25g
Full table for chopped celery

Where these numbers come from

USDA FoodData Central, SR Legacy, food 11143: “Celery, raw”. USDA lists these household measures for it:

1 cup chopped = 101g
1 NLEA serving = 110g
1 tbsp = 7.5g
1 stalk, large (11"-12" long) = 64g
1 stalk, medium (7-1/2" - 8" long) = 40g
1 stalk, small (5" long) = 17g
1 strip (4" long) = 4g

Fractions of a cup are the cup weight scaled down. The teaspoon is a third of the tablespoon. Metric-cup figures assume a 250ml cup, and Australian tablespoons hold 20ml. Weights under 10g are rounded to 0.1g, everything else to the nearest gram. Full source list.