What Is a Printing Calculator?

A printing calculator (also called an adding machine or tape calculator) is a desktop device that performs arithmetic while simultaneously printing results on a paper roll. They're widely used in accounting, retail, bookkeeping, and anywhere a physical record of calculations is needed.

If you've just acquired one for home, office, or study use, this guide will walk you through everything you need to get started.

Getting to Know the Keys

Before you start calculating, familiarise yourself with the main key groups:

  • Number keys (0–9): Enter digits just as you would on a standard calculator.
  • Arithmetic keys (+, −, ×, ÷): Perform the four basic operations.
  • = or Total key: Finalises and prints the result.
  • CE / C key: Clears the current entry without losing your running total.
  • CA / AC key: Clears everything, including the running total — use with caution.
  • +/− key: Changes the sign of the number entered (positive to negative).
  • % key: Calculates percentages.
  • GT (Grand Total) key: Accumulates the totals of multiple calculations.
  • Tax+ / Tax− keys: Add or subtract a pre-set tax rate.

Step-by-Step: Basic Addition

  1. Turn on the machine and ensure paper is loaded.
  2. Enter your first number using the number keys (e.g., 245).
  3. Press the + key. The number prints on the tape.
  4. Enter your next number (e.g., 182).
  5. Press + again to add it to the running total.
  6. Repeat for all numbers in your list.
  7. Press = or the Total key to print the final sum.

Step-by-Step: Subtraction

  1. Enter the starting amount and press +.
  2. Enter the amount to subtract.
  3. Press the − key instead of +.
  4. Press = to see the result.

Calculating Percentages

Most printing calculators handle percentages in a slightly different way from standard calculators. To find a percentage of a number:

  1. Enter the base number (e.g., 500).
  2. Press ×.
  3. Enter the percentage (e.g., 15).
  4. Press %. The result (75) prints automatically.

Using the Tax Function

Many modern printing calculators have a built-in tax rate you can set once and reuse:

  1. Enter the tax rate (e.g., 20) and press the Tax Rate Set button (often accessed via a shift or mode key — check your manual).
  2. To apply tax to a price, enter the price and press Tax+. The display shows the tax-inclusive total.
  3. To remove tax from a price, press Tax− to extract the pre-tax amount.

Managing the Paper Tape

  • Use standard 57mm or 58mm thermal paper rolls for most desktop printing calculators.
  • When the paper runs low, a red stripe appears at the edge — replace the roll promptly.
  • To load new paper: lift the paper cover, place the roll so paper feeds from the bottom, feed it into the slot, and press the paper-feed button until it emerges from the print head.
  • Keep printed tapes for record-keeping — the printout is a reliable audit trail for bookkeeping.

Tips for Efficient Use

  • Use the GT (Grand Total) key to tally multiple separate calculations without re-entering numbers.
  • The decimal selector switch controls how many decimal places are shown — set it to 2 for currency.
  • The rounding switch (usually 5/4, ↑, or ↓) determines how the machine rounds results.
  • Always double-check your tape after a long calculation session — errors in entry are easy to spot on the printed record.