Calculates how much energy passes from one trophic level to the next in a food chain, using the commonly taught “10% rule.”
How it works
The starting energy is multiplied by the transfer efficiency raised to the power of the number of trophic levels climbed.
What this does not include
The 10% figure is a widely cited average approximation, not an exact law — real transfer efficiency varies by ecosystem and species, commonly cited in the 5-20% range.
How to use this calculator
- Enter the starting energy, how many trophic levels up you’re measuring, and the transfer efficiency (10% by default).
A worked example
10,000 kcal of energy at the producer level, transferring up 1 trophic level at 10% efficiency: energy available = 10,000×0.10 = 1,000 kcal.
The same starting energy, transferring up 2 levels at 10% efficiency each: energy available = 100 kcal — each additional level compounds the loss.
What the variables mean
| Variable | Meaning |
|---|---|
| Energy | Starting energy at the base trophic level |
| Levels | How many trophic levels the energy passes through |
| Efficiency | Percentage of energy transferred at each level, commonly around 10% |
Edge cases worth knowing
Energy loss compounds with each trophic level. Two levels at 10% efficiency each isn’t a 20% loss — it’s a 99% loss overall (10% × 10% = 1% remaining), which is exactly why food chains rarely extend beyond four or five levels.
An efficiency over 100% has no biological meaning — no real trophic transfer creates more energy than it started with, so the calculator declines to show a result for that input.
Frequently asked questions
Why is so much energy lost between trophic levels?
Most energy is lost as metabolic heat, used for movement and bodily functions, or simply never consumed (as inedible parts or waste) rather than being converted into new consumer biomass.
Why do food chains rarely have more than four or five levels?
Because each level loses about 90% of the energy from the one below it, so there’s simply not enough energy left to support many additional levels near the top.
Does this explain why there are fewer apex predators than prey animals?
Yes — the dramatic energy loss at each level is exactly why ecosystems can only support a much smaller biomass of top predators than of the plants and herbivores beneath them.
