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Road Gradient Calculator

Road gradient = rise ÷ horizontal length × 100. A road climbing from RL 100.000 at chainage 0 to RL 106.500 at chainage 250 m rises 6.5 m in 250 m: a 2.6% grade, or 1 in 38.5 (1.49°). Keeping within an 8% maximum, that rise needs at least 81 m of road.

Inputs

Results update as you type.

Start point
m
m
End point
m
m
Design check
Road profileRL 100 mRL 107 m250 mGrade 2.6% up · max 8%myconstructioncalculator.comNot to scale
Diagram updates as you type.

Results

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Road gradient (uphill)
2.60%
Ratio1 in 38.5
Angle1.49 °
mm per metre26.0 mm/m
Rise / fall6.500 m
Horizontal length250.00 m
Length needed at 8.0%81.3 m OK
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Working
  1. Rise = 106.500 m − 100.000 m = 6.500 m; length = 250.00 m − 0.00 m = 250.00 m
  2. Gradient = rise ÷ length × 100 = 2.600%
  3. At most 8.0%, the level change needs at least 81.3 m of road
Results are estimates for planning and material ordering only. They are not a substitute for structural design or approval by a qualified engineer. Read the full disclaimer.
Formula


Gradient (%)   = (RL end − RL start) ÷ (chainage end − chainage start) × 100
1 in N         = horizontal ÷ rise
Angle          = arctan(rise ÷ horizontal)
Length needed  = rise ÷ maximum grade


Worked Example


Chainage 0 at RL 100.000 m to chainage 250 m at RL 106.500 m:


    

  1. Rise = 6.500 m over 250 m
    2. 

  2. Gradient = 6.5 ÷ 250 × 100 = 2.60% = 1 in 38.5 = 1.49°
    3. 

  3. At an 8% maximum the climb needs at least 6.5 ÷ 0.08 = 81.3 m
    4. 



Gradient Conversions






Percent
1 in N
Degrees






1%
1 in 100
0.57°




2%
1 in 50
1.15°




5%
1 in 20
2.86°




8%
1 in 12.5
4.57°




10%
1 in 10
5.71°




12%
1 in 8.3
6.84°




15%
1 in 6.7
8.53°






Frequently Asked Questions
How do you calculate road gradient?
Divide the difference in level by the horizontal distance between the two points and multiply by 100 for a percentage. 6.5 m of rise over 250 m is 2.6%.
What is a 1 in 20 gradient as a percentage?
5%. Divide 100 by the second number: 1 in 10 is 10%, 1 in 50 is 2%.
What is the maximum gradient for a road?
It depends on the road class, design speed, terrain and local standard, often around 5–8% for main roads and higher for short sections on minor or mountain roads. Use the limit set by your road authority.
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