Free tools for researchers — no signup
30+ calculators, statistical tables, and reference guides — the things researchers otherwise google: sample sizes, critical values, effect size benchmarks, reporting checklists. Built on the same engines that power Kahubi.
Plan your study
Design decisions before you collect a single data point: the right test, the right n, a clean randomization.
Which statistical test should I use?
Answer a few questions about your design and get the right test, linked to its calculator.
Sample size calculator
Respondents needed for a survey at your margin of error and confidence level, with finite population correction.
Sample size for two groups
A priori power analysis for a two-group design: n per group from effect size, α, and power.
Sample size table (Krejcie & Morgan)
Population → required sample size at 95% confidence, ±5% — the classic 1970 table, computed live.
Random group generator
Randomly assign participants to 2–10 balanced groups — seeded and reproducible.
Statistics calculators
Paste your data, get the full result table, an interpretation, and a copy-ready APA sentence.
Descriptive statistics
Mean, SD, median, IQR, min/max and skewness for any column of numbers.
One-sample t-test
Does your sample mean differ from a known value μ? t, df, p, Cohen’s d.
Independent t-test
Compare the means of two separate groups. Welch’s t, p, Cohen’s d.
Paired t-test
Pre/post or repeated measures on the same cases. t, p, Cohen’s d_z.
One-way ANOVA
Compare means across 3+ groups. F, df, p and η² effect size.
Chi-square test
Association between two categorical variables from a table of counts.
Pearson correlation
Linear relationship between two variables. r, r², p-value.
Spearman correlation
Rank-based association — robust to outliers and ordinal scales.
Mann–Whitney U
Nonparametric two-group comparison for skewed or ordinal data.
Cronbach’s alpha
Scale reliability (α) with item–total diagnostics.
Effect sizes, intervals & p-values
Work from summary statistics — no raw data needed.
Effect size (Cohen's d)
Cohen's d, Hedges' g and r from group means and SDs — with CI, benchmarks, and an APA sentence.
Confidence interval
CI for a mean (t-based) or a proportion (Wilson) from summary statistics — no raw data needed.
p-value from a test statistic
Exact p from a t, z, chi-square or F value — one- or two-tailed, with the APA sentence.
Cohen's kappa (inter-rater)
Agreement between two raters beyond chance — paste both raters’ codes, get κ with CI and interpretation.
Statistical tables
The printed tables from the back of the textbook — computed exactly, with live lookups for any df.
z-table (standard normal)
Cumulative normal probabilities, common critical values (1.96, 2.576…), and an exact z lookup.
t-table (critical values)
Critical t values by df and α, one- and two-tailed, plus an exact lookup for any df.
Chi-square table
Critical χ² values for df 1–100 across all common significance levels, with exact lookup.
F-table (ANOVA)
Critical F values at α = .05 and .01 by numerator and denominator df, with exact lookup.
Writing & reporting
Word limits, readability, checklists, symbols, and the abbreviation rules reviewers mark up.
Word counter + readability
Words, characters, sentences, Flesch scores, and progress against abstract word limits.
Reporting guidelines lookup
CONSORT, PRISMA, STROBE, COREQ & co. — which checklist your study design needs, with links.
Effect size benchmarks
Small/medium/large cutoffs for d, r, η², kappa, Cronbach's α, ICC — with conversions and caveats.
Statistical symbols reference
M vs μ, s vs σ, p, α, β, η² and every other statistical symbol — meanings plus APA typesetting.
Latin abbreviations guide
e.g. vs i.e., et al., ibid., cf., sic and 25 more — meanings, punctuation, and style rules.
Systematic review
References
BibTeX ⇄ RIS converter
Convert reference files between BibTeX (LaTeX) and RIS (EndNote, Zotero, Mendeley) — both directions.
Citation generator
Format references in APA, MLA, Chicago, Harvard, IEEE or Vancouver — from BibTeX/RIS or manual fields.
Find a paper’s PDF
Look up a DOI or title and get legal open-access PDF links from OpenAlex and Semantic Scholar.
Why these tools are free
Every tool on this page wraps an engine from Kahubi, the AI workspace for research: the statistics calculators and tables run the exact same distribution code our in-app analysis flow uses, the PRISMA generator renders the same diagram our systematic-review flow produces automatically from your screening decisions, and the reference tools share our library import/export code. They run with no account and no usage limits — your pasted data is processed in your browser and never stored. If they save you time, the full workspace (your library, drafts, datasets and an agent that works across them) is one click away.
Or just ask the AI
Every question these tools answer — and the follow-ups they can't — the AI inside Kahubi handles with your own data and library as context.
Free accounts include AI chat, literature search, and every tool on this site.
Want the analysis written up, not just computed?
In Kahubi, the AI agent runs statistics on your uploaded dataset, screens papers for your review, and drafts the write-up in your own style — with your library as context.