I understand that the Swadhisthana chakra is located in the sacral region. Does it encompass the whole hip or only the small space of a circumference of maybe 2-3 centimeters?
How far-does- the swadhisthana chakra extend?
The Devi Bhagavata Purana gives us some clues about Svādhiṣṭhāna Chakra. From the information given in the book by the author/ translator it looks like that the **Svādhiṣṭhāna chakra is upto the root of the the genital organs called prostatic plexus (Linga Mula).**So its quite possible that this chakra is extended upto upto the root of the the genital organs .
इडया वायुमारोप्य पूरयित्वोदरे स्थितम् | शनैः षोडशमात्राभिरन्यया तं विरेचयेत् । ॥ ४१ ॥
एवं सधूमः प्राणानामायामः कथितो मुने | आधारेलिङ्गनाभिप्रकटितहृदये तालुमूले ललाटे ॥ ४२ ॥
द्वे पत्रे षोडशारे द्विदशदशदलद्वादशार्धे चतुष्के । वासान्ते बालमध्ये डफकतसहिते कण्ठदेशे स्वराणां |
हंक्षंतत्त्वार्थयुक्तं सकलदलगतं वर्णरूपं नमामि ॥ ४३ ॥
अरुणकमलसंस्था तद्रजःपुञ्जवर्णा | हरनियमितचिह्ना पद्मतन्तुस्वरूपा ।
रविहुतवहराकानायकास्यस्तनाढ्या | सकृदपि यदि चित्ते संवसेत्स्यात्स भुक्तः ॥ ४४ ॥
38-49 Now the process of piercing the six Cakras (or nerve centres or centres of moving Prānik forces) is being described. Within this body, the six nerve centres called Padmas (Lotuses) exist. They are respectively situated at the (1) Mūlādhāra (half way between Anus and Liṅga Mūla), called the Sacral Plexus; (2) Liṅga Mūla (the root of the genital organs); called postatic plexus; (this is also called Svādhiṣṭhāna) (3) Navel, the Solar Plexus (4) Heart, the cardiac Plexus, (5) Throat (6) Forehead, between the eye brows there; the lotus in the forehead, called the cavernous plexus (Ājñā Cakra) has two petals; in these two petals, the two letters “Ham” “Kṣam” exist in the right hand direction (with the bands of the watch;
Please note that this is not the precise expert answer. And is just the answer based on information found in the text. More accurate answer can be given by looking in the texts which are authoritative on this topic.