Surprisal Calculator
Free online surprisal calculator. Enter your values and get instant results with the formula, step-by-step working, a worked example and FAQs — everything runs locally in your browser on Calcton, no signup required.
中文版：自信息计算器
原理：自信息（惊奇度）I = −log2 p——概率越小的事件发生时携带的信息越多。掷出均匀硬币正面 I = 1 比特，掷中 1/10 的事件 I ≈ 3.32 比特，必然事件 I = 0。log2 的底 2 决定了单位是比特，换自然对数就是奈特。
步骤：① 输入事件概率；② 点击计算；③ 读出比特数与等效状态数。
示例：p = 0.1 时 I = 3.321928094887 比特，等效于在约 10 个等概率结果中指定其一；p = 0.5 时 I = 1 比特。
注意事项：p 必须大于 0——概率为 0 的事件自信息无穷大，因为「不可能事件居然发生」无法用有限比特描述；独立事件的自信息相加，对应联合概率相乘；多个事件的自信息平均就是香农熵。
相关：信息熵计算器把自信息按概率加权平均；KL 散度计算器比较两个分布的信息差异；密码熵计算器用同样的比特度量评估密码强度。
How to use the Surprisal Calculator
- Fill in the inputs with your own numbers — every field shows what it expects.
- The result updates instantly as you type; no "Calculate" click needed.
- Read the result card for the main figure, the step-by-step formula, and practical notes.
Frequently asked questions
Is the Surprisal Calculator free?
Yes — all math calculators on Calcton are free, with no sign-up required. Your inputs are processed in your browser and never sent to a server.
Is there a Chinese version of this tool?
Yes. Use the Chinese version link above — it is the same calculator with the interface in Simplified Chinese.
References
Formulas and benchmarks used by this calculator follow these published sources.
KevinContent LeadCalcton Editorial Team · Last updated 2026-10-06
Kevin maintains Calcton's formula verification and content: every calculator cites the standard it implements, worked examples are recomputed programmatically, and health benchmarks follow WHO and international guidelines.
Related calculators
More in this category: Math calculators
About math calculators
Free online math calculators for algebra, statistics, number theory and everyday arithmetic — from quadratic equations and matrices to percentages, fractions and prime factorization, each with step-by-step formulas.