Measure the rise: the vertical height from the ground to the surface your dog steps onto (car cargo floor, sofa seat, bed top). Then enter the ramp's usable length. The calculator treats the ramp as the sloping side of a right triangle, so angle = asin(rise ÷ length).
How long a ramp do I need?
For your rise, these are the ramp lengths that give each reference angle (length = rise ÷ sin(angle)):
Which angle is "safe"?
We show 18, 20 and 25 degrees because they are the figures most often quoted online. They are not a veterinary standard: an evidence review by Mobility Dog Guide found no veterinary guideline or peer-reviewed study that sets one universal safe angle for dog ramps. A gentler slope is generally easier for a stiff or nervous dog, and surface grip, side rails and ramp width also matter. Ask your vet or a rehabilitation vet about your dog.
See our dog ramp angle and length chart for worked examples by car type, and our guides to SUV ramps and sedan ramps and steps.
Calculations run in your browser; nothing is sent or stored. Results are approximate: ramp hooks, lips and soft ground change the real angle.