Learn

Tools and resources for learning and practice.

Accounting

Allowance for Doubtful Accounts Calculator Estimate the allowance for doubtful accounts from accounts receivable using a percentage of the receivable balance on a 0-100 scale.
APIC Excess Par Issuance Calculator Split share issuance proceeds between common stock at par and additional paid-in capital for the excess over par.
Asset Turnover Calculator Calculate total asset turnover as net sales divided by average total assets, measuring how efficiently assets generate revenue.
Bonus Accrual Monthly Recognition Calculator Accrue a bonus expense monthly straight line from a bonus target and percentage: per-month expense and the cumulative accrued amount after elapsed months.
Cash Conversion Cycle Calculator Calculate the cash conversion cycle in days as days inventory outstanding plus days sales outstanding minus days payable outstanding.
Deferred Revenue Straight-Line Recognition Calculator Recognize deferred revenue straight line by month: per-month revenue, amount recognized after elapsed months, and the remaining deferred balance.
Depletion of Natural Resources Calculator Compute depletion expense for a natural resource from units extracted using a per-unit rate of cost minus salvage value divided by estimated total units.
Disposal Gain or Loss Calculator Determine the gain or loss on disposing of a depreciable asset: book value as cost minus accumulated depreciation, then sale proceeds minus book value.
DSO Days Sales Outstanding Calculator Calculate days sales outstanding as average accounts receivable divided by credit sales, times the number of days in the period.
EBITDA from Net Income Addbacks Calculator Calculate EBITDA as net income plus interest, taxes, depreciation, and amortization addbacks, all from the same period and currency.
Free Cash Flow Calculator Calculate free cash flow as net cash provided by operating activities minus capital expenditures for the same period and currency.
Inventory Turnover Calculator Calculate inventory turnover as cost of goods sold divided by average inventory, measuring how often inventory is sold and replaced per period.
LIFO Reserve Disclosure Calculator Compute the LIFO reserve as FIFO minus LIFO inventory with its deferred tax effect and after-tax impact for disclosure.
Operating Cycle Calculator Calculate the operating cycle in days as days sales in inventory plus days sales outstanding, the time from acquiring inventory to collecting cash from sales.
Payable Turnover and Days Calculator Calculate payable turnover and payment days from credit purchases and average accounts payable for the same period and currency.
Percentage of Completion Calculator Recognize construction revenue to date under the cost-to-cost percentage-of-completion method: costs incurred divided by estimated total costs times the contract price.
Retained Earnings Rollforward Calculator Roll retained earnings forward for a period: beginning balance plus net income (or minus a net loss) minus dividends declared.
Times Interest Earned Calculator Calculate times interest earned as operating income (EBIT) divided by interest expense, measuring how many times current earnings cover interest obligations.
Units-of-Production Depreciation Rate Calculator Compute the units-of-production depreciation rate per unit as cost minus salvage value divided by estimated total units of output.
Useful Life Revision Calculator Compute revised annual straight-line depreciation after a useful-life estimate change: book value at revision minus revised salvage, divided by remaining years, applied prospectively.

Acoustics

Activation

Actuarial

Agriculture

Growing Degree Days Calculator Accumulate growing degree days from daily high and low temperatures after clipping both observations to caller-selected lower and upper thresholds.

Algebra

Approximation

Vertex-Cover 2-Approximation Demonstrator Build a maximal matching and select both endpoints to obtain an unweighted vertex cover with a factor-2 guarantee.

Aquaculture

Archival Studies

Arithmetic

Astronomy

Auditing

Aviation

Biology

Bitwise

Calculus

Carpentry

Cartography

Chart

Cheatsheets

Check

Checksum

Chemistry

Cipher

Clustering

Color

Combinatorics

Construction

Convert

Cooking

Cryptography

Css

CSS Length to Pixels Convert px, rem, em, vw, and vh CSS lengths to pixels using explicit root, element, and viewport dimensions; unsupported units are rejected.

Csv

CSV Pivot Table Tool Aggregate CSV rows into a deterministic grouped pivot table.

Data Analysis

Archetypal Analysis Demonstrator Approximate multivariate observations as convex mixtures of archetypes that are themselves mixtures of the observations.

Data Structure

Date

Decode

JWT Decoder Decode a JWT's header and payload from base64url JSON and report the signature bytes; the signature is never verified, so status is always unverified.

Demography

Development

Diagram

Dictionary

Translate a Word Translate an English word into German, French, or Japanese using a locally cached, attributed starter dictionary.

Distance

Document

LaTeX as Document Wrap LaTeX equation markup in a structured Tool.io document.

Electricity

Electronics

Engineering

Epigraphy

Estimation

Particle Filter Estimator Estimate a one-dimensional hidden state with a reproducible bootstrap particle filter.

Film

Filter

Hacker News Filter Search recent Hacker News stories and filter them by story type, date, points, comments, or topic.

Fitness

Forestry

Game Search

Game Theory

Generate

Geo

Geodesy

WGS84 Semi Major Lookup Return the WGS84 ellipsoid semi-major axis in metres for the requested realisation.

Geography

Geojson

Geology

Geometry

Graph

Hash

Health

Horology

Http

Information

Interpolation

Json

Laser

Lighting

Linguistics

List

Logic

SAT Formula to CNF Converter Convert a Boolean JSON syntax tree to equisatisfiable CNF clauses with Tseitin auxiliary variables. Supported operators are variable, NOT, AND, OR, and implication; integer literals use negative signs for negation.

Logistics

Machine Learning

Math

Matrix

Meteorology

Microcontroller

Mortgage

Music

Mycology

Nautical

Network

Neural Network

Feedforward Neural Network Demonstrator Run one dense neural-network layer with selectable activation entirely in the browser.

Normalize

Number

Numismatics

Nutrition

Oenology

Online Algorithm

Online Ski-Rental Algorithm Demonstrator Compare a deterministic online rent-or-buy strategy with the optimal decision made in hindsight.

Optimization

Paleography

Parasitology

Parse

Password

Password Strength Estimate offline-attack strength from character-class pool size and length, never storing or transmitting the secret.

Pathfinding

A* Pathfinding Visualizer Find and inspect a shortest path through a JSON grid using A* search.

Periodic Table

Physics

Probability

Proportions

Random

Real Estate

References

Regex

Regex Escape Escape regular-expression metacharacters so arbitrary text can be embedded safely in a RegExp.

Regression

Reinforcement Learning

Render

Code Renderer Edit highlighted HTML, CSS, and JavaScript examples and render the result locally in a sandboxed live preview.

Repl

SQLite REPL Run SQLite commands locally in your browser with tabular results and a database that persists for the current session.

Roadmap

Sailing

Search

Beam Search Visualizer Expand a scored tree breadth-first while retaining only the highest-scoring paths at each depth.

Security

PEM Block Inspector Inspect PEM armored text for block metadata only: BEGIN/END labels, decoded byte counts, and RFC 1421 header line count; no ASN.1 parsing.

Seismology

Semiconductor

Sequence

Set

Similarity

Sociology

Sports

Statistics

Stochastic Process

Tax

Progressive Tax Calculator Calculate marginal tax bands, total tax, and effective and marginal rates from an explicit bracket schedule.

Text

Thesaurus

Tool.io

tool.io icons Browse and filter the first-party functional SVG icons used across tool.io interfaces.

Tools

Trading

Trading Market Hours Show the regular Sydney, Tokyo, London, and New York forex sessions and their date-specific overlaps in a selected time zone.