RecallWeaveOffline teaching explorer

Let the units do the work.

Changing units changes a number, while the quantity stays the same. Follow the scale factors, inspect the dimension powers, and see why a centimetre squared needs a squared conversion.

Worked guide and answersOpen the learner

Choose a quantity

Start with a conversion you can predict, then change one part.

Decimal or scientific notation, such as 2.5 or 1e-3.

Use * or / between units, ^ for a whole power, and parentheses for a denominator: kg/(m*s^2). Case matters.

Try a different idea

Keeps the entered expressions, dimension powers, exact fractions and display precision. Download a fresh copy after changing a value.

Predict, change, explain

  1. Choose Area. If 1 cm is 10 mm, what must happen to each of two length factors?
  2. Choose Speed. Why does the hour-to-second factor belong in the denominator?
  3. Choose Prefix case. Compare MJ with mJ without changing the underlying energy.
  4. Choose A mismatch. What information besides a scale factor would connect length with time?

What this check can tell you

Matching dimensions permit a scale conversion for the listed units. They do not prove that a physical equation is correct, determine a numerical constant, or tell you what kind of quantity is being described.

For example, energy and torque share the same base dimensions but describe different quantities. Interpret your calculation in its physical context.

Arithmetic treats your entered number as exact. It does not estimate measurement uncertainty or select significant figures from an experiment. Affine temperatures, logarithmic units and arbitrary formulas are outside this explorer.

Supported symbols and exact scales

Use explicit multiplication: m*s means metre × second; ms means millisecond. Division proceeds from left to right: kg/m*s differs from kg/(m*s). μm also accepts µm or the typed spelling um; ², ³ and · are accepted conveniences. Other symbols are not inferred.

Each row gives one listed unit in metre, kilogram and second units.
SymbolNameExact base-unit scale

Expression limits: 128 characters, 24 unit factors, four levels of parentheses, whole powers from −6 to 6, and combined dimension powers from −24 to 24. The numerical value accepts at most 24 decimal digits, including zeros, and a scientific exponent from −24 to 24. The exact-number size is bounded.

Continue in the twelve-question lesson

Download the lesson above. Open RecallWeave, choose the JSON under Bring your own lesson, inspect the preview, and select Start this deck. Explanations, practice retries and downloadable study notes use the existing learner.

The explorer and its two downloads work directly from this HTML file, offline. The guide and learner links open separate supplied files; keep the repository folder structure to use those links. Inputs stay in this page and are not saved automatically.