| Local Name | Lumia 638 |
| Technology | GSM / HSPA / LTE |
| 4G Bands | LTE band 3(1800), 7(2600), 38(2600), 39(1900), 40(2300), 41(2500) |
| 3G Bands | HSDPA 850 / 900 / 1900 / 2100 - RM-1010 |
| 2G Bands | GSM 850 / 900 / 1800 / 1900 |
| Speed | HSPA 42.2/5.76 Mbps, LTE Cat4 150/50 Mbps |
| GPRS | Yes |
| EDGE | Yes |
| Announced | 2014, December |
| Status | Available. Released 2014, December |
| Dimensions | 129.5 x 66.7 x 9.2 mm (5.10 x 2.63 x 0.36 in) |
| Weight | 136 g (4.80 oz) |
| SIM | Micro-SIM |
| Display Type | IPS LCD capacitive touchscreen, 16M colors |
| Screen Size | 4.5 inches, 55.8 cm2 (~64.6% screen-to-body ratio) |
| Resolution | 480 x 854 pixels, 16:9 ratio (~218 ppi density) |
| Protection | Corning Gorilla Glass 3 | ClearBlack display |
| OS | Microsoft Windows Phone 8.1 |
| Chipset | Qualcomm Snapdragon 400 (28 nm) |
| CPU | Quad-core 1.2 GHz Cortex-A7 |
| GPU | Adreno 305 |
| Card Slot | microSD, up to 256 GB (dedicated slot) |
| Internal Memory | 8 GB, 1 GB RAM |
| Camera Features | Panorama |
| Video | Yes |
| Loudspeaker | Yes |
| 3.5mm Jack | Yes |
| Sound | Active noise cancellation with dedicated mic |
| WLAN | Wi-Fi 802.11 b/g/n, DLNA, hotspot |
| Bluetooth | 4.0, A2DP, LE/ aptX after WP8 Denim update |
| GPS | Yes, with A-GPS, GLONASS |
| Radio | FM radio |
| USB | microUSB 2.0 |
| Sensors | Accelerometer |
| Battery | Removable Li-Ion 1830 mAh battery (BL-5H) |
| Colors | Black |
| SAR EU | 1.46 W/kg (head) 0.95 W/kg (body) |
