Low-FODMAP Macro Calculator for IBS & SIBO
The low-FODMAP diet (Monash University, 2005) removes short-chain carbohydrates that ferment in the intestine: Fermentable Oligosaccharides, Disaccharides, Monosaccharides And Polyols. It's the most evidence-backed dietary intervention for irritable bowel syndrome (IBS) and SIBO, improving symptoms in 70% of patients. The standard macro distribution is 20% protein / 30% fat / 50% carbohydrates, with carbs sourced exclusively from low-FODMAP foods. The protocol has 3 phases: 1) Elimination (2–6 weeks); 2) Gradual reintroduction (6–8 weeks); 3) Personalisation.
On the low-FODMAP diet the standard macro split is **20% protein / 30% fat / 50% carbohydrates**, but carbs must come from low-FODMAP sources only (rice, potato, oats, ripe banana). For 2,000 kcal/day: 100 g protein + 67 g fat + 250 g tolerated carbs.
When to use this calculator
- Diagnosed IBS (irritable bowel syndrome).
- Confirmed SIBO (breath test).
- Chronic bloating and gas.
- Multiple food intolerances.
- Your gastroenterologist or dietitian recommended it.
Worked example: 2,000 kcal/day low-FODMAP plan
- Daily calories: 2,000 kcal.
- Protein (20%):
2000 × 0.20 / 4= 100 g/day — chicken, meat, fish, eggs. - Fat (30%):
2000 × 0.30 / 9= 67 g/day — olive oil, avocado, aged cheese. - Low-FODMAP carbs (50%):
2000 × 0.50 / 4= 250 g/day — rice, potato, carrot, quinoa, ripe banana.
How it works
2 min readWhat is the Low-FODMAP Diet?
Developed at Monash University (Australia), low-FODMAP temporarily removes short-chain carbohydrates that gut bacteria rapidly ferment, producing gas, bloating, and pain.
The 5 FODMAP Groups to Restrict
| Group | High-FODMAP Foods |
|---|---|
| Fructans | Wheat, onion, garlic, leek |
| GOS | Legumes, broccoli, beetroot |
| Lactose | Milk, yogurt, ricotta |
| Excess fructose | Apple, mango, honey, pear |
| Polyols | Cherries, sorbitol, xylitol |
Allowed Low-FODMAP Foods
| Category | Options |
|---|---|
| Grains | Rice, potato, quinoa, oats (½ cup cooked), polenta |
| Protein | Chicken, beef, fish, eggs, firm tofu |
| Vegetables | Tomato, cucumber, carrot, spinach, squash |
| Fruit | Strawberry, ripe banana, kiwi, orange, grapes |
| Dairy | Lactose-free options, aged cheese (cheddar, parmesan) |
| Fats | Olive oil, small portion of avocado |
Macro Table by Calorie Level
| Calories | Protein | Fat | Carbs |
|---|---|---|---|
| 1,500 kcal | 75 g | 50 g | 188 g |
| 1,800 kcal | 90 g | 60 g | 225 g |
| 2,000 kcal | 100 g | 67 g | 250 g |
| 2,200 kcal | 110 g | 73 g | 275 g |
| 2,500 kcal | 125 g | 83 g | 313 g |
The 3 Phases of the Monash Protocol
Phase 1 – Elimination (2–6 weeks)
Remove all high-FODMAP foods completely. Most patients see significant symptom relief within 1–2 weeks.
Phase 2 – Reintroduction (6–8 weeks)
Test one FODMAP group at a time: 3 test days (increasing portions) followed by 3 washout days. Identifies which specific groups trigger your symptoms.
Phase 3 – Personalisation
Avoid only the groups that caused symptoms. Many people can reintroduce most foods after completing the protocol.
Scientific Evidence
Related Tools
Not a permanent diet. Long-term FODMAP elimination can negatively affect gut microbiota diversity. Always work with a registered dietitian.
Frequently asked questions
What is the standard low-FODMAP macro split?
The Monash University protocol uses 20% protein, 30% fat, and 50% carbohydrates as the starting distribution. The key constraint is that carbs must come from low-FODMAP sources — not from wheat, onion, garlic, legumes, or high-fructose foods.
How many grams of carbs on low-FODMAP for 2,000 kcal?
At 2,000 kcal with 50% carbs: 2000 × 0.50 / 4 = 250 g of carbohydrates per day, from tolerated sources like rice, potato, quinoa, oats (½ cup cooked), ripe banana, strawberries, and carrots.
How long does the elimination phase last?
2 to 6 weeks, depending on symptom severity. It's not recommended to extend beyond 6–8 weeks because prolonged elimination can reduce gut microbiota diversity.
Does the low-FODMAP diet cure IBS or SIBO?
It doesn't cure either condition, but improves symptoms in 70% of IBS patients (2017 meta-analysis). For SIBO, it works best when combined with antibiotic or herbal antimicrobial treatment prescribed by your doctor.
Can vegetarians or vegans follow low-FODMAP?
It's challenging but possible. Most plant proteins (legumes, seitan) are high-FODMAP. Tolerated options: firm tofu (not silken), tempeh (small portions), canned and rinsed chickpeas or lentils (max ¼ cup). A dietitian familiar with low-FODMAP is essential.
What is Phase 2 and why does it matter?
Phase 2 is the reintroduction phase (6–8 weeks). You test one FODMAP group at a time: 3 test days with increasing portions, then 3 washout days before testing the next group. This identifies which specific groups trigger your symptoms — most people are sensitive to only 1–2 groups, not all.
What's the best app for checking FODMAP foods?
The Monash FODMAP app (official, iOS and Android) is the gold standard — 1,000+ foods with red/yellow/green ratings by serving size. Also useful: FODMAP Friendly app.
Is low-FODMAP a permanent eating plan?
No. Elimination is temporary (2–6 weeks). After completing Phase 2 reintroduction, Phase 3 personalises your diet — most people avoid only the 1–3 groups that trigger their specific symptoms and eat freely otherwise.