Fiber Intake Calculator
Fibre requirements scale with how much you eat rather than with body size, because fibre's role is bound up with the volume of food passing through. The standard guideline is 14 grams per 1,000 calories, which is what this calculator applies.
Your result
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Why fibre scales with calories
Unlike protein or fluid, fibre targets are conventionally expressed relative to energy intake rather than body weight. The reasoning is that fibre works in proportion to the food it accompanies — its effects on transit, satiety and glycaemic response are all tied to the meal it is part of.
The practical consequence catches people out during weight loss: eating less lowers your fibre target in absolute terms, but it also removes the foods that were supplying it. Intake tends to fall faster than the target does.
- Soluble fibre forms a gel that slows digestion — oats, legumes, apples, citrus.
- Insoluble fibre adds bulk and speeds transit — wholegrains, vegetable skins, nuts and seeds.
- Most whole plant foods provide both, in varying proportions, which is why variety beats supplementation.
- Most people in Western countries eat well under the guideline figure, so a shortfall is the norm rather than the exception.
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Increase it gradually, and with fluid
A sudden large increase in fibre reliably causes bloating, gas and discomfort. Gut bacteria adapt to a change in substrate over a couple of weeks, and jumping straight to a target rather than climbing toward it is the single most common reason people conclude fibre does not agree with them.
Fibre also needs fluid to do its job. Insoluble fibre works by drawing water in to add bulk; without adequate fluid it can make constipation worse rather than better. If you are increasing fibre specifically to address constipation, increasing fluid alongside is not optional.
This matters particularly for anyone whose digestion is already slowed. Adding a large amount of fibre on top of delayed gastric emptying, without correspondingly more fluid, tends to produce the opposite of the intended result.
Frequently asked questions
This calculator is general information for healthy adults, not medical or dietary advice. It applies published population formulas and cannot account for your clinical situation. Where a clinician has set you a target, that target replaces this one.
Built by the Pep AI team.