Measuring Tips and Techniques for People with Reduced Vision
By Gil Johnson
One of the challenges facing people with reduced vision is taking accurate accurate measurements. For persons with some vision or no vision at all, this can seem like a real barrier. However, there are several ways to take good measurements if you have difficulty seeing the markings on a ruler or tape measure.
Tip: Measure twice; cut once!
Using Everyday Materials to Measure
Estimating Measurements Without Using a Ruler
- One inch is approximately the distance from the first knuckle to the fingertip.
- Four inches is approximately the width of the hand along the base of the fingers.
- Eighteen inches is approximately the distance from the elbow to the fingertips, with the arm outstretched.
One- and Three-Foot Rulers and Retractable Tape Measures
- Most hardware stores or home supply centers have one-foot rulers or three-foot yardsticks. Sometimes they are free or are quite inexpensive. These may have large enough markings so that you may be able to read them if you have low vision.
- If you can’t read the numbers, ask a friend or family member to make a notch along one edge at one-inch increments and on the other edge in half-inch increments. This can enable you to use your fingernail to count the notches and get a reasonably accurate measurement.
- You can use a piece of string to measure available space. Tie a knot in the string at the length you want to measure and lay the string along a ruler or tape measure to determine the length.
- Make a dark pencil mark or use a push pin on a one-foot ruler or yardstick to indicate the available space.
- If you have some remaining vision, you may be able to read the markings in better lighting, or you can ask a family member or friend to read the measurement for you.
Tip: If you have low vision, improved lighting can sometimes enable you to read the markings on rulers. For more information about selecting lighting, see Home Modifications.
- Most retractable tape measures have a built-in lock. You can lock the tape at the measurement you want and read it in better lighting or ask a family member or friend to read the measurement to you.
Locking tape measure
Specialized Measuring Tools
Several types of measuring devices have been adapted or designed for use by persons with low vision or no vision. Most are easy to use and allow for fairly accurate measurements.
Rulers and Yardsticks
- One-foot rulers and three-foot yardsticks with pre-made tactile markings at 1/4, 1/2, and 1 inch
- One-foot rulers with large print and/or braille markings
A one-foot ruler with tactile and braille markings
You can find sources for these measuring tools in the Assistive Products category in the VisionAware Directory of Services.
The Click Rule
The Click Rule is a metal tubular device slightly longer than 7 1/2 inches. A 7-inch threaded rod is inserted into the tube. A knurled locking knob is screwed into the top of the threaded rod through a long slot that has been machined into the tube.
The Click Rule
As the threaded rod is extended into and out of the tube, a clicking sound can be heard at 1/16-inch intervals. The threaded rod has raised threads every 1/2 inch.
The metal tube has two flat rectangular stops or fences mounted on it. One stop or fence is located precisely at the open end of the tube and the raised thread rod protrudes through it. The other stop or fence is positioned exactly six inches along the tube from the stop at the open end of the tube.
The Click Rule comes with three 12-inch extension rods that screw into the end of the Click Rule raised thread rod and into each other, enabling accurate measurements at 1/16-inch intervals, from zero to four feet. Additional extension rods can enable measurements beyond four feet.
Click Rule with a one-foot extension rod
The Click Rule can be purchased from the National Federation of the Blind Online Store and from Community Advocates Inc., P.O. Box 83304, Lincoln, NE 68501-3304; 402-486-3091.
The Rotomatic Rule
The Rotomatic Rule consists of a 6 1/2 inch threaded steel rod with a large rotating rectangular measuring nut or fence that can be moved precisely along the threads and locked in place with a six-sided hexagonal locking nut.
Rotomatic Rule fully extended
The 3/8 inch diameter threaded rod has raised threads at every 1/2-inch interval to facilitate feeling the scale.
A full turn of the measuring nut moves it 1/16 inch, a half turn moves it 1/32 inch, a quarter turn moves it 1/64 inch.
Rotomatic’s narrow end
The Rotomatic comes with three extension rods of 6 inches, 12 inches and 18 inches that screw into the Rotomatic threaded steel rod as well as into each other.
The Rotomatic Rule can be purchased from the National Federation of the Blind Online Store and from Community Advocates Inc., P.O. Box 83304, Lincoln, NE 68501-3304; 402-486-3091.
Talking Tape Measure
The Talking Tape Measure is a 16-foot retractable tape measure that has been modified to give a measurement reading in synthetic speech.
Speech is available in the following languages: English, French, Italian, Norwegian, Spanish, and Swedish.
The Talking Tape Measure can be purchased from Cobalt Systems Limited.