Indian phone number formats
India's numbering plan assigns 10-digit numbers for mobile phones (starting with 6, 7, 8 or 9) and variable-length numbers for landlines (2–4 digit STD code + 6–8 digit number, totalling 10 digits). The trunk prefix 0 is used for domestic dialing and is dropped in international format.
| Format as entered | Type | E.164 output |
|---|---|---|
| 9876543210 | Mobile (10-digit) | +919876543210 |
| 09876543210 | Mobile with trunk prefix | +919876543210 |
| 91 98765 43210 | Mobile with country code, spaces | +919876543210 |
| +91-98765-43210 | Mobile with +91 and hyphens | +919876543210 |
| 0091 9876543210 | Mobile with 00 prefix | +919876543210 |
| 022 2457 1234 | Mumbai landline with STD code | +912224571234 |
| 080-2550-1234 | Bengaluru landline with STD code | +918025501234 |
Mobile vs landline detection
After stripping the trunk prefix and country code, mobile numbers are exactly 10 digits and start with 6, 7, 8 or 9. Landline numbers also total 10 digits (STD code + subscriber number) but start with 2, 3, 4 or 5 (the STD code).
The tool uses this distinction to validate: a 10-digit number starting with 0 or 1 is invalid for India. Numbers shorter than 10 digits after cleaning (like an old 8-digit Delhi number without the STD code) are flagged for manual review.
Common formatting problems in Indian phone data
- Inconsistent prefix — the same list has 9876543210, +919876543210 and 09876543210.
- Spaces and hyphens inserted at different positions — +91 98765 43210 vs +91-9876-543210.
- Country code without plus — 919876543210 looks like a 12-digit number but is actually +91 + 10 digits.
- Excel scientific notation — long numbers like 919876543210 become 9.19877E+11 and lose digits.
- Mixed countries — a few international numbers in a mostly Indian list get wrongly prefixed with +91.
- Landline without STD code — 24571234 (8 digits) is a Mumbai number but needs 022 to be complete.
Why E.164 matters for Indian businesses
Most Indian businesses use WhatsApp Business, Zoho PhoneBridge, Freshcaller, Exotel or similar platforms for customer communication. All of these require or prefer E.164 format (+91XXXXXXXXXX). CRMs like HubSpot, Zoho and Salesforce display and match phone numbers correctly only when they're in a consistent international format.
For bulk WhatsApp messaging via the WhatsApp Business API, numbers must be in E.164. A list with mixed formats — some with +91, some without, some with 0 — causes delivery failures and wasted API credits.