Important distances between Shimla / Kullu Manali are:

Delhi to Shimla 370 km (9 hours by road)

Delhi to Manali 570 km (14 hours by road)

Chandigarh to Shimla 120 km ‘(4 hours by road)

Chandigarh to Manali 320 km (9 hours by road)

Kalka to Shimla 96 km (3 1/2 hours by road)

Shimla to Manali 270 km (8-9 hours by road)

Shimla to Kullu 230 km (7-8 hours by road)

Kullu to Manali 40 km (1 hour by road)

Traveling time remains a big factor and entire day has to be kept for traveling from one destination to the other.

Since Shimla happens to be the nearest destination from Delhi and Chandigarh, traveling to Shimla first is advisable.