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Gut Transit Time and Microbiome Diversity Score

Calculate your estimated Gastro-Transit time (hours) and microbiome diversity level. This tool uses the Bristol Stool Scale, daily fiber intake, and the 30 Plants rule to estimate your gut health and stability.

Enter Values

Bristol Stool Scale (1-7)

Visual guide to stool consistency and transit speed.

Weekly Plant Variety (Types)

0100

Number of different plant types eaten in 7 days (fruits, veg, nuts, seeds, grains, legumes, herbs).

Daily Dietary Fiber (g)

Total grams of fiber consumed daily.

Fermented Foods (times/week)

Frequency of eating yogurt, kimchi, sauerkraut, kefir, or kombucha.

Daily Water Intake (L)

Daily consumption of plain water.

Result

Enter values above and click Calculate to see your result.

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Formula

Core Formula

\text{Stability Score} = 0.35 \left(\frac{P}{30}\right) + 0.25 \left(\frac{F}{30}\right) + 0.20 \left(\frac{Fer}{7}\right) + C + H

How it works: The Microbiome Stability Score is a weighted index: 35% for plant variety (diversity), 25% for fiber intake (prebiotics), 20% for fermented food frequency (probiotics), 15% for stool consistency (transit quality), and 5% for hydration. Transit time is estimated using the Bristol Stool Scale adjusted for dietary fiber and water.

Review and Methodology

Updated Apr 12, 2026

This calculator runs locally in your browser. Inputs are converted into the units required by the formula, and the result is paired with supporting references so you can verify the method before using it for planning or estimates.

Worked Example

A user with: 20 plants/week, 25g fiber, 3 fermented servings, BSS Type 4, and 2.0L water.

1. Diversity: (20/30) x 35 = 23.3

2. Fiber: (25/30) x 25 = 20.8

3. Fermentation: (3/7) x 20 = 8.6

4. Consistency (Type 4): 15

5. Hydration: (2/2.5) x 5 = 4.0

Total Stability Score: 71.7/100 (High Stability)

Estimated Transit: ~35 Hours (Optimal)

Understanding Gut Transit and the Microbiome Ecosystem

Your gut is a complex ecosystem. Two critical markers of health are transit time, which is how long food stays in your system, and microbiome diversity. Chronic slow transit (constipation) can lead to the reabsorption of waste, while very fast transit may prevent nutrient absorption. Diversity, tracked by the 30 Plants rule, measures the variety of beneficial bacteria that protect your immune system and metabolic health.

Bristol Stool Scale: A medical tool used to classify stool consistency into seven types. Type 4 is considered the global gold standard for healthy digestion.
The 30 Plants Rule: Research suggests that individuals who eat 30 or more different types of plants per week have a significantly more diverse and resilient microbiome compared to those who eat 10 or fewer.
Prebiotic Fiber: Fiber is the fuel for your good bacteria. A target of 25 to 30 grams daily is ideal for maintaining bulk and moisture in the digestive tract.
Fermented Foods: These introduce beneficial probiotics into the ecosystem to help maintain a stable acidic environment and crowd out harmful pathogens.

This tool is for educational purposes and provides an estimation based on dietary habits. It is not a clinical diagnostic tool. If you have chronic digestive pain or significant changes in habits, consult a gastroenterologist.

You can also calculate changes using our BMI Calculator, Macro Calculator, Calorie Calculator or Protein Needs Calculator.

Microbiome Diversity and Transit Benchmarks

Plant Count	Diversity Level	Health Impact
Under 10	Low	High risk of metabolic and immune instability
11 to 20	Moderate	Standard western profile; room for improvement
21 to 30	High	Associated with diverse short-chain fatty acids
Over 30	Exceptional	Peak resilience and microbiome health marker

Note: Transit time targets vary by individual but generally fall between 24 and 72 hours for optimal health.

Frequently Asked Questions

What is a healthy gut transit time?

For most healthy adults, a normal transit time ranges from 24 to 72 hours. While speed varies, consistently being under 12 hours or over 96 hours may indicate underlying issues like malabsorption or chronic constipation.

Why are 30 plants a week the magic number?

The American Gut Project found that 30 is the threshold where microbiome diversity plateaus. People eating 30+ plants had higher levels of healthy bacteria and lower levels of antibiotic-resistant genes.

Does coffee or tea count as a plant?

Yes, coffee beans and tea leaves count toward your plant variety because they contain polyphenols that feed beneficial bacteria. Herbs and spices also count, but variety is more important than quantity for the score.

How can I increase my fiber intake safely?

Increase fiber slowly (3 to 5 grams per week) and significantly increase water intake at the same time. Rapidly adding fiber without enough water can cause bloating and temporary constipation.

What is the most accurate way to measure transit time?

While this calculator provides an estimate based on stool consistency, the gold standard is a Blue Poop Test (using blue food coloring) or a Sitzmarker study conducted by a medical professional.

Can I have high diversity with slow transit?

It is possible but difficult. Slow transit allows opportunistic bacteria to overgrow, which can reduce the dominance of beneficial species. Moving the gut regularly is key to a fresh and stable microbiome.

Can I embed this Gut Transit Time and Microbiome Diversity Score on my website?

Yes. Click the "Embed" button at the top of this page to customize the size, colors, and theme, then copy the iframe code. Paste it into any HTML page, WordPress site, or CMS. It is completely free, requires no signup, and works on all devices. You can also visit our embed guide at calculory.com/services/embed-calculators for more details.

Medical Disclaimer

This calculator is provided for informational and educational purposes only. It is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making any decisions based on these results. Do not disregard or delay seeking medical advice because of information obtained from this tool.

AI Assistant

Ask about this calculator

I can help you understand the gut transit time and microbiome diversity score formula, interpret your results, and answer follow-up questions.

Try asking

Our AI assistant provides general estimates and advice only. Please consult a qualified healthcare professional before making any health-related decisions.

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