Vol. 12 · 119 tools, indexed · Updated daily
A complete
reference
for everyday
calculation,
from kilograms
to mortgages.
119 calculators and converters, arranged on a single page so you never click twice. Quiet typography, exact arithmetic, no advertising.
111
calculators
8
converters
0
categories
In rotation today — Mortgage payment, BMI, Celsius ↔ Fahrenheit, Tip & split, Date difference, Compound interest, kg ↔ lb.
Editor's picks · Spring 2026
№ 01 · ToolTorus Surface Area CalculatorCalculate the surface area of a torus using major radius R and minor radius r with the formula A = 4π²Rr.Open the tool№ 02 · ToolTorus Volume CalculatorCalculate the volume of a torus (donut shape) using major radius and minor radius with the formula V = 2π²Rr².Open the tool№ 03 · ToolTrapezoidal Prism Volume CalculatorCalculate the volume of a trapezoidal prism using base dimensions, trapezoid height, and prism depth. Ideal for drainage channels, storage bins, and construction projects.Open the tool№ 04 · ToolCollatz Conjecture CalculatorCalculate Collatz Conjecture (3n+1) sequences: see stopping time, max values, and complete iteration paths for any positive integer starting point.Open the tool
From the editors
What we mean
by “exact”.
Every conversion on terican uses constants ratified by the Bureau International des Poids et Mesures, computed in arbitrary precision and rounded only at the moment of display.
Calculators are open source, audited annually, and accompanied by their formulas in plain language — because a calculator that hides its arithmetic is just a magic trick.