How To Measure Grade
2008-06-01 (updated 2012-02-02)
How much you can carry and how quickly it can be done is often determined by the "ruling grade", the steepest hill that will be encountered on a particular trip. I find that people (myself included!) often seriously overestimate the actual value of grades they regularly encounter. This causes them to believe they need overly-complex and expensive gearing and braking systems, when standard equipment will usually suffice.
Knowing the value of common grades in your area also allows you to calculate how much you can carry using your bike.
Measuring and calculating grade is simple and requires only a level and ruler. For accurate measurements, you will want a level at least 18-24" (45-60 cm) long. If you don't have access to one that long, you can tape or rest the level on a straight edge instead.
- Rest the level (or straight edge) on the ground. Lift up the lower end of the level/straight edge (i.e, the end nearest the bottom of the hill) until the level measures level.
- While holding the level/straight edge still in this position, measure the distance between the end of the level and the ground using the ruler, as shown in the image below.
- Calculate the grade by dividing the distance measured with the ruler (the "rise") by the length of the level or straight edge (the "run") and multiplying by 100:
% grade = (rise / run ) X 100
Measuring the grade of a street
In the image above, the end of this 18" long level, when it is horizontal, is about 1-1/2" above the roadway. Using the formula above:
grade = 1.5" / 18" x 100 = 8.3%
Of course, you will get the same result regardless if both measurements are in inches or centimeters.
To make it easier, the table below lists the grade calculated for some common lengths of levels:
| Length of Level ("Run") | |||||
|---|---|---|---|---|---|
| 18" | 24" | 36" | 48" | ||
| Distance Measured with Ruler ("Rise") | 1/8" | 1% | 1% | 0% | 0% |
| 1/4" | 1% | 1% | 1% | 1% | |
| 3/8" | 2% | 2% | 1% | 1% | |
| 1/2" | 3% | 2% | 1% | 1% | |
| 5/8" | 3% | 3% | 2% | 1% | |
| 3/4" | 4% | 3% | 2% | 2% | |
| 7/8" | 5% | 4% | 2% | 2% | |
| 1" | 6% | 4% | 3% | 2% | |
| 1 1/8" | 6% | 5% | 3% | 2% | |
| 1 1/4" | 7% | 5% | 3% | 3% | |
| 1 3/8" | 8% | 6% | 4% | 3% | |
| 1 1/2" | 8% | 6% | 4% | 3% | |
| 1 5/8" | 9% | 7% | 5% | 3% | |
| 1 3/4" | 10% | 7% | 5% | 4% | |
| 1 7/8" | 10% | 8% | 5% | 4% | |
| 2" | 11% | 8% | 6% | 4% | |
| 2 1/8" | 12% | 9% | 6% | 4% | |
| 2 1/4" | 12% | 9% | 6% | 5% | |
| 2 3/8" | 13% | 10% | 7% | 5% | |
| 2 1/2" | 14% | 10% | 7% | 5% | |
| 2 5/8" | 15% | 11% | 7% | 5% | |
| 2 3/4" | 15% | 11% | 8% | 6% | |
| 2 7/8" | 16% | 12% | 8% | 6% | |
| 3" | 17% | 12% | 8% | 6% | |
| 3 1/8" | 17% | 13% | 9% | 7% | |
| 3 1/4" | 18% | 14% | 9% | 7% | |
| 3 3/8" | 19% | 14% | 9% | 7% | |
| 3 1/2" | 19% | 15% | 10% | 7% | |
| 3 5/8" | 20% | 15% | 10% | 8% | |
| 3 3/4" | 21% | 16% | 10% | 8% | |
| 3 7/8" | 22% | 16% | 11% | 8% | |
| 4" | 22% | 17% | 11% | 8% | |
| 4 1/8" | 23% | 17% | 11% | 9% | |
| 4 1/4" | 24% | 18% | 12% | 9% | |
| 4 3/8" | 24% | 18% | 12% | 9% | |
| 4 1/2" | 25% | 19% | 12% | 9% | |
| 4 5/8" | 26% | 19% | 13% | 10% | |
| 4 3/4" | 26% | 20% | 13% | 10% | |
| 4 7/8" | 27% | 20% | 14% | 10% | |
| 5" | 28% | 21% | 14% | 10% | |
| 5 1/8" | 28% | 21% | 14% | 11% | |
| 5 1/4" | 29% | 22% | 15% | 11% | |
| 5 3/8" | 30% | 22% | 15% | 11% | |
| 5 1/2" | 31% | 23% | 15% | 11% | |
| 5 5/8" | 31% | 23% | 16% | 12% | |
| 5 3/4" | 32% | 24% | 16% | 12% | |
| 5 7/8" | 33% | 24% | 16% | 12% | |
| 6" | 33% | 25% | 17% | 12% | |
Categories: Cargo Biking