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Last updated: Aug 9, 2026

Firehouse Subs

Onion

Large Sub ToppingsPopular

Firehouse Subs Onion is carb-leaning, with about 88% of macro calories from carb. Each serving has 19 calories, 0.5g protein, 4.5g carbs, and 0g fat, making it a lighter restaurant option to compare with larger meals.

8 Rings

Serving Size

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Calories

Per serving

0.5 g

Protein

4.5 g

Carbs

0 g

Fat

Nutrition Facts

Amount per serving

Calories19 kcal

% Daily Value*

Total Fat 0 g0%

Saturated Fat 0 g0%

Trans Fat 0 g—

Cholesterol 0 mg0%

Sodium 2 mg0%

Total Carbohydrate 4.5 g2%

Dietary Fiber 0.8 g3%

Total Sugars 2 g—

Protein 0.5 g1%

Vitamin A—

Vitamin C—

Vitamin D—

Calcium—

Iron—

Potassium—

Caffeine—

* The % Daily Value tells you how much a nutrient in a serving contributes to a daily diet.

Nutrition Breakdown

kcal

Protein0.5 g (10%)

Carbs4.5 g (88%)

Fat0 g (2%)

Estimated calorie contribution using 4 kcal/g for protein and carbohydrates and 9 kcal/g for fat.

Meal Planning Insights

Protein density2.7/10

10% of macro calories come from protein.

Satiety index3.8/10

Estimated from protein, fiber, calories, and fat balance.

Activity estimate5 min walk

About 2 minutes of running for these calories.

Key Nutrients

Protein 0.5 g1%

Fiber 0.8 g3%

Sodium 2 mg0%

Sugars 2 g—

Saturated Fat 0 g0%

How we calculate these values

Diet Compatibility

High protein2.7/10 protein density from 0.5g protein and 19 calories.No

Lower carb4.5g carbs per serving.Yes

Low fat0g total fat per serving.Yes

High sugar2g total sugars per serving.No

High sodium2mg sodium per serving.No

Vegetarian source flagNo vegetarian flag is published for this item.Not flagged

Ingredients

ONION

Similar Items in Large Sub Toppings

View all

Au Jus Bell Peppers5 kcal · 0.2 g protein Au Jus Mushrooms10 kcal · 1.2 g protein Avocado160 kcal · 2 g protein

Compare with other items

Select up to 3 items to compare calories, protein, sodium, and macros.

Quick comparisons

Onion has 131 fewer calories than 1% Chocolate Milk and 6.5g less protein. Compare

Onion has 71 fewer calories than 1% Milk and 6.5g less protein. Compare

1% Chocolate Milk150 kcal · 7 g protein1% Milk90 kcal · 7 g protein5-Cheese Mac & Cheese380 kcal · 17 g proteinApple Juice100 kcal · 0 g proteinAu Jus Bell Peppers5 kcal · 0.2 g proteinAu Jus Bell Peppers3 kcal · 0.1 g protein

Compare with 1% Chocolate Milk

Onion Compared With Nearby Items

Compared with Au Jus Mushrooms, another Large Sub Toppings item at Firehouse Subs, Onion has 9 more calories than it and 0.7g less protein than it. That makes this page useful for deciding between nearby menu choices, not just reading a raw nutrition label.

Data Source and Methodology

Nutrition values for Onion are maintained in Nutrimetry from restaurant-published menu data and were last checked on Aug 9, 2026. Macro percentages use 4 calories per gram for protein and carbohydrates and 9 calories per gram for fat.

Read the data methodology

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