Measuring an area and a volume with a laser distance meter
What does the area function calculate?
Two readings, one multiplication. Aim at a wall and confirm; aim at the wall at right angles to it and confirm; the instrument shows the product in square metres. Nothing a tape measure and a calculator could not do — except that you copy nothing down and never read the wrong line.
Both distance meters in the range do this, with a different reach and a different memory.
And the volume?
Three readings: length, width, height. The result comes out in cubic metres. That is the figure you need to size heating, ventilation or a dehumidifier, and it is also the one people calculate worst in their heads. The arithmetic happens inside the instrument, on no paper at all.
How much error do the stated ±2 mm leave?
A room 4.20 m by 3.10 m is 13.02 m². With ±2 mm on each length, the result stays between 13.005 m² and 13.035 m²: three hundredths of a square metre of spread in all. The instrument's uncertainty is therefore negligible beside the uncertainty of the gesture.
| What you measure | Result | Spread from the ±2 mm |
|---|---|---|
| A length of 4.20 m | 4.20 m | ±2 mm |
| Area 4.20 × 3.10 m | 13.02 m² | ±0.015 m² |
| Volume 4.20 × 3.10 × 2.50 m | 32.55 m³ | ±0.06 m³ |
Put another way: at the scale of a tin of paint or a heating calculation, the instrument’s accuracy does not show. What does show is a beam that hit the skirting board instead of the wall, or a corner that is not square.
Where is the reference point?
A distance meter measures from its front or from its back, as you choose, and you have to tell it which. Held against a wall you measure from the back; set on the edge of an opening, from the front. It is the setting easiest to forget.
A correct reading with the wrong reference point gives an error equal to the length of the body — 120 mm on the 80 m model.
How do you add several rooms together?
Both instruments add and subtract readings and keep the results in memory: 99 readings on the 80 m model, 30 on the green 120 m. Measure each room, add them up, and you have the area of a floor without writing a line. Subtraction is for openings: wall area minus window area.
Which of the two, for what use?
Both distance meters measure distance, area and volume to the same stated accuracy of ±2 mm. Three things really separate them: the range, the angle measurement and the power source. The table puts them side by side, and the paragraph after it says which to choose for what you are measuring.
| Feature | 80 m | 120 m green |
|---|---|---|
| Stated reach | 80 m | 120 m |
| Stated accuracy | ±2 mm | ±2 mm, in 0.5 s |
| Quantities measured | distance, area, volume | distance, area, volume, angle |
| Memory | 99 readings | 30 readings |
| Power | batteries, not included | rechargeable battery, USB-C |
For surveying rooms the 80 m is enough, and its memory is larger. The green 120 m adds angle measurement and a green beam, visible to the naked eye far further than a red one — that is what you need as soon as you go outdoors or work in large volumes.
See also: distance meter or tape measure, angle measurement and Pythagoras, and our laser distance meters.
- Area = two readings, volume = three: the instrument does the multiplying.
- The stated ±2 mm give ±0.015 m² on 13.02 m² and ±0.06 m³ on 32.55 m³ — negligible.
- The reference point, front or back, is worth the length of the body: 120 mm on the 80 m model.
- Memory: 99 readings on the 80 m, 30 on the green 120 m.