Shop Fraction Calculator

Feet · Inches · Fractions · Millimetres

Getting Started with the Shop Fraction Calculator

Type a sum the way you'd say it in the shop, such as 5' 3 1/2" + 7/8 − 12mm, and read the answer as a tape fraction, feet and inches, decimals and millimetres. Use it to add up a run of parts, take a reveal off an opening, split a length into equal parts, or convert a metric plan. The Calculate tab does the arithmetic; the Convert tab turns millimetres into the nearest fraction and back, and prints a conversion chart.

Calculate

  1. Type in the Entry box, or tap the keypad under it (handy on a phone in the shop). The answer shows under the box as you type, or a note about what's wrong. Keypad tips, beside the Entry heading, shows the keys to tap for fractions, mixed numbers, millimetres and feet.
  2. Write measurements the shop way: 12, 12.5, 3/4, 5 1/2 or 5-1/2, feet with ' or ft, inches with " or in, and mm, cm or m. Feet and inches go together: 5' 3 1/2" or 5'-3 1/2".
  3. Do the arithmetic with + − × ÷ (or * and /) and brackets. Multiplying and dividing come before adding and subtracting, so (96 − 1 1/2) ÷ 4 needs its brackets.
  4. Read the answer under Answer: decimals, metric, and the nearest 1/8", 1/16", 1/32" and 1/64", each with its margin. Round to in Settings picks the fraction shown under the entry, on the tape and in the badge, which says whether the exact length is a little Strong (past the mark) or Shy (short of it), and by how much.
  5. Read it off the tape under On the Tape: the mark to measure to, with inches along the top edge and millimetres along the bottom.
  6. Keep a running tape: press = or Enter to add the sum to the Tape and carry its answer on in the entry, ready for the next step. Press an answer on the tape to put it back in the entry. Clear Tape empties it. The tape and settings are kept in this browser only.
  7. Working in metric? Set Plain numbers to mm, so a number without a unit counts as millimetres instead of inches.

Convert

  1. Pick a direction under Convert: mm → in or in → mm, then type the length (or tap the keypad). A plain number is in the unit you're converting from.
  2. mm → in gives the nearest fraction at your Round to setting, what that fraction is in mm, and a table of the nearest 1/8", 1/16", 1/32" and 1/64" with the margin for each, so you can see which lands closest.
  3. in → mm gives the exact millimetres and the nearest 1 mm, 0.5 mm and 0.1 mm mark with the margin for each. Round mm to picks the one the badge and the tape use.
  4. Print the Conversion Chart with Print Chart: every fraction up to an inch in mm, and each millimetre to 50 mm with its nearest fraction. It follows Round to, so pick 1/16" for a short chart or 1/64" for a full one.

Key terms

Plain number
A number with no unit. Added to a length, or on its own, it counts as inches (or mm, if you choose). Multiplying or dividing by one scales a length: 3 1/2 × 4 is 14".
Strong and shy
Shop talk for a length a hair past the mark (strong) or a hair short of it (shy). Round to a finer fraction to get closer.
Margin
How far the exact length is past (+) or short of (−) a mark, in mm and inches. A positive margin is strong, a negative one shy.
Length ÷ length
Gives a plain number, how many times one fits in the other: 96" ÷ 3 1/2" is 27.43, so 27 whole pieces before kerf.

Assumptions

  • A space or a hyphen with no spaces joins a whole number to a fraction: 5 1/2 and 5-1/2 are both five and a half. With spaces round it, 5 - 1/2 subtracts.
  • Inches after feet are always inches, even when plain numbers are millimetres.
  • The calculator works out lengths and plain numbers, not areas: multiplying two lengths is an error.
  • The fraction is rounded to the nearest mark; the decimal and metric answers are exact (to the decimals shown). Saw kerf is not taken off anything.

Questions or feedback

If a number looks wrong, a step is confusing, or you have an idea, email [email protected]. Include what you entered so the numbers can be checked.

Open this guide again any time with the Getting Started button.

Answer

The nearest fraction at every precision, with how far the exact length is past (+) or short of (−) it. Your Round to row is highlighted; the decimals and metric are exact.

Strong by 0.0276" (0.7 mm)
Decimal Inches63.9026"
Decimal Feet5.3252'
Millimetres1623.1 mm
Centimetres162.31 cm
NearestFractionFeet & InchesMargin inMargin mm
1⁄8"63 7⁄8"5' 3 7⁄8"+0.0276+0.7
1⁄16"63 7⁄8"5' 3 7⁄8"+0.0276+0.7
1⁄32"63 29⁄32"5' 3 29⁄32"−0.0037−0.09
1⁄64"63 29⁄32"5' 3 29⁄32"−0.0037−0.09

On the Tape

636416016116216316463 7⁄8"1623.1 mm

Tape

Press = or Enter to add a sum here. Press an answer to put it back in the entry. Kept in this browser only.

Nothing on the tape yet.

About the Shop Fraction Calculator

Add, subtract, multiply and divide feet, inches, fractions and millimetres the way you'd say them, like 5' 3 1/2" + 7/8 − 12mm. Round the answer to the nearest 1/8" to 1/64", see how strong or shy that is, and read it off a drawn tape. Convert millimetres to the nearest fraction and back, with the margin at every precision, and print a conversion chart.