Free online calculators

Estimates the token cost of an image for OpenAI vision models from its width, height and detail level.

Animated support-desk model using Erlang C that shows waits exploding near full utilisation and how much an extra agent helps.

Czech income tax calculator for individuals (Czech language).

Web calculator for estimating and comparing LLM API costs across models.

Simulates Warhammer 40,000 attack dice and shows hit, wound and save probabilities as charts.

Works out which trades rebalance a portfolio while limiting taxes.

Computes timer prescaler and compare values for AVR timer interrupts on Arduino.

Backtests an asset allocation, showing returns, volatility and drawdowns.

Relates signal rise time to bandwidth and the trace length at which it acts like a transmission line.

Estimates how long a battery will last for a given load current.

Estimates distance to a Bluetooth device from RSSI and path loss exponent.

German gross-to-net salary calculator (German language) for 2026 taxes and social contributions.

Counts Monday to Friday working days between two dates, with your own holidays excluded.

Finds reactions, shear, moment and deflection for a cantilever beam.

Gives stored energy and time constant for a capacitor with a series resistor.

Estimates tax owed on long-term and short-term investment gains.

Backtests a retirement withdrawal plan against historical returns and inflation.

Calculates resistor values that set the thresholds of a comparator with hysteresis.

Shows savings growth for daily, monthly or yearly compounding.

Compounded balance of a deposit over a chosen number of years and compounding period.

Official US calculator for buying-power change between two months using CPI data.

Six date tools in one page: date difference, duration, age, workdays and date arithmetic.

Counts the days, weeks and months between two dates.

Estimates what an appliance costs to run from its wattage, daily hours and price per kWh.