In terms of relative calorie burn, running burns roughly 130% more calories than walking.
Below is a more accurate calorie burn for running vs walking (the difference between the 2).
Calories Burned based on Time and Weight.
Calories Burned in 1 hour
Weight 100lb:214
Weight 120lb:257
Weight 125lb:268
Weight 150lb:321
Weight 175lb:375
Weight 200lb:429
Weight 250lb:536
Weight 300lb:643
Calories Burned in 40 minutes
Weight 100lb:143
Weight 120lb:171
Weight 125lb:179
Weight 150lb:214
Weight 175lb:250
Weight 200lb:286
Weight 250lb:357
Weight 300lb:429
Calories Burned in 40 minutes
Weight 100lb:143
Weight 120lb:171
Weight 125lb:179
Weight 150lb:214
Weight 175lb:250
Weight 200lb:286
Weight 250lb:357
Weight 300lb:429
Calories Burned in 45 minutes
Weight 100lb:161
Weight 120lb:193
Weight 125lb:201
Weight 150lb:241
Weight 175lb:281
Weight 200lb:321
Weight 250lb:402
Weight 300lb:482
Calories Burned in 1 hour 30 mins
Weight 100lb:321
Weight 120lb:386
Weight 125lb:402
Weight 150lb:482
Weight 175lb:563
Weight 200lb:643
Weight 250lb:804
Weight 300lb:964
Calories Burned in 2 hours
Weight 100lb:429
Weight 120lb:514
Weight 125lb:536
Weight 150lb:643
Weight 175lb:750
Weight 200lb:857
Weight 250lb:1072
Weight 300lb:1286