---
title: "Lloyd’s bound · Library · Simulation Hypothesis"
url: https://simulation-hypothesis.com/library/lloyd-bound
description: "Lloyd’s bound is the physical limit on computing found by Seth Lloyd (2000)."
license: https://creativecommons.org/licenses/by/4.0/
credit: "Ross Allan Dahl, Simulation Hypothesis (simulation-hypothesis.com)"
---

## Physics & computation

# Lloyd’s bound

Definition

Lloyd’s bound is the physical limit on computing found by Seth Lloyd (2000). He worked out from quantum mechanics that one kilogram of matter can do at most about 5 × 10^50 elementary operations per second. For the observable universe that comes to roughly 10^104 operations per second, and 10^120 over cosmic history.

On this site

The universe-computer rung: all matter working at the physical maximum. It’s the top of the machine ladder.

Role in the model

Lloyd’s bound is the ceiling on the machine ladder. It makes a universe-scale computer a real physical object and not just a figure of speech. All the mass in the observable universe, computing at the physical limit, gives about 10^104 operations per second. Several sandbox scenarios need more than that. That’s what “physics says no” means here.

Related

[FLOPS](https://simulation-hypothesis.com/library/flops)[Landauer limit](https://simulation-hypothesis.com/library/landauer-limit)[Bekenstein bound](https://simulation-hypothesis.com/library/bekenstein-bound)

## The people behind the terms

14 short pages, one per thinker, each with its matching dial. See also the [reading list](https://simulation-hypothesis.com/reading).

[Plato’s cave](https://simulation-hypothesis.com/thinkers/plato)[Zhuangzi’s butterfly](https://simulation-hypothesis.com/thinkers/zhuangzi)[Vasubandhu’s dream](https://simulation-hypothesis.com/thinkers/vasubandhu)[Shankara’s māyā](https://simulation-hypothesis.com/thinkers/shankara)[al-Ghazali’s doubt](https://simulation-hypothesis.com/thinkers/ghazali)[Ibn Arabi’s imagination](https://simulation-hypothesis.com/thinkers/ibn-arabi)[Calderón’s life is a dream](https://simulation-hypothesis.com/thinkers/calderon)[Descartes’ demon](https://simulation-hypothesis.com/thinkers/descartes)[Berkeley’s perceiver](https://simulation-hypothesis.com/thinkers/berkeley)[Borges’ circular ruins](https://simulation-hypothesis.com/thinkers/borges)[Nozick’s experience machine](https://simulation-hypothesis.com/thinkers/nozick)[Putnam’s brain in a vat](https://simulation-hypothesis.com/thinkers/putnam)[Bostrom’s trilemma](https://simulation-hypothesis.com/thinkers/bostrom)[Chalmers: virtual worlds are real](https://simulation-hypothesis.com/thinkers/chalmers)