Horlobase
enfrde

Tudor · Black Bay

Tudor Black Bay 31 S&G

Reference M79603-0001 · Classic · 31 mm

Ø 31 mmLug-to-lug 37.8 mm
Illustration drawn from the specifications: case to scale, colours and style approximate. Not a photo. Photos on the official page

Specifications

Reference
M79603-0001
Family
Black Bay
Category
Classic
Status
Current
Case material
Steel and yellow gold
Case diameter
31 mm
Case thickness
9.5 mm Official
Lug-to-lug
37.8 mm Third-party
Lug width
17 mm Official
Water resistance
100 m
Bezel
Fixed, smooth
Certifications
COSC
Calibre
MT5201 Official
Power reserve
about 50 h

Official product page · retrieved October 15, 2026

Does it fit your wrist?

Enter your wrist circumference. The watch appears to scale on the flat top of the wrist.

Lug-to-lug 37.8 mmFlat top of the wrist 54.1 mm
Top view on a wrist, to scale
Flat top of the wrist 54.1 mmLug-to-lug 37.8 mmCase diameter 31 mm
Side view, across the wrist

Looks small

Lug-to-lug 37.8 mm on a flat top of 54.1 mm: 70 % of the width.

Lug-to-lug is under 75% of the flat top. Fine to wear, but the watch may look small on you.

Measurements and sources

Brands rarely publish thickness, lug width and lug-to-lug together. Each observation below is kept separate, with who gave it.

Case thickness

Value Type Source Date
9.5 mm Official Tudor October 15, 2026

Lug-to-lug

Value Type Source Date
37.8 mm Third-party Everest Bands Strap retailer size guide (December 2023), model-level figure listed for refs 79600, 79603. October 14, 2026

Lug width

Lug width is the gap between the lugs, where the strap fits. It is not lug-to-lug.

Value Type Source Date
17 mm Official Tudor October 15, 2026

Calibre source

Official Tudor · retrieved October 15, 2026

Other versions in the same case

These references differ only by dial, bracelet or bezel colour. The brand gives them the same case dimensions, so the figures on this page apply to them too.

Other Black Bay references

Watch Ø Thickness Lug-to-lug Calibre
Black Bay 31 M79600-0001 31 mm 9.5 mm 37.8 mm MT5201
Black Bay 36 S&G M79643-0001 36 mm 10.5 mm 43.9 mm MT5400
Black Bay 36 M79640-0002 36 mm 10.5 mm 43.9 mm MT5400
Black Bay 39 S&G M79663-0001 39 mm 12 mm 47.3 mm MT5602
Black Bay 39 M79660-0002 39 mm 12 mm 47.3 mm MT5602
Black Bay 41 M79680-0002 41 mm 12.2 mm 50.2 mm MT5601
Black Bay M7941A1A0NU-0003 41 mm 12.7–13.6 mm⚠ 49–50 mm⚠ MT5602-U
Black Bay Ceramic M7941A1ACNU-0001 41 mm 13.6 mm 49 mm MT5602-U
Black Bay Ceramic (MT5602-1U) M79210CNU-0001 41 mm 14.4 mm 50 mm MT5602-1U

Other Tudor models

Watch Ø Thickness Lug-to-lug Calibre
Royal 30 S&G M2830A1A3-0003 30 mm 8.7 mm — MT5201
Clair de Rose 30 M35500-0009 30 mm 10.7 mm — T201
Royal 30 M2830A1A0-0001 30 mm 8.7 mm — MT5201
1926 28 M91350-0011 28 mm 9.1 mm — T201
1926 28 S&G M91351-0011 28 mm 9.1 mm — T201
Clair de Rose 34 M35800-0009 34 mm 11.1 mm — T601
Show 34 more
Watch Ø Thickness Lug-to-lug Calibre
Royal 36 S&G M2836C1A3-0002 36 mm 9.7 mm — MT5412
1926 36 M91450-0001 36 mm 9.2 mm — T601
Clair de Rose 26 M35200-0009 26 mm 10.3 mm — T201
Royal 36 M2836C1A0-0102 36 mm 9.7 mm — MT5412
Royal 40 S&G M2840D1A3-0002 40 mm 11.4 mm — MT5633
1926 M91650-0001 41 mm 9.3 mm — T601
1926 39 M91550-0001 39 mm 9.2 mm — T601
1926 Luna M91560-0002 39 mm 10.1 mm — T607-9
Monarch M2639W1A0U-0001 39 mm 11.9 mm — MT5662-2U
Royal M2840D1A0-0001 40 mm 11.4 mm — MT5633
Ranger 36 M79930-0007 36 mm 11 mm — MT5400
Northflag M9140G1A0U-0001 40 mm 12.7 mm — MT5652-U
Ranger M79950-0001 39 mm 12 mm 47 mm MT5402
Black Bay Chrono S&G M79363N-0001 41 mm 14.4 mm 50 mm MT5813
Black Bay GMT S&G M79833MN-0001 41 mm 14.6 mm 50 mm MT5652
Black Bay 54 M79000B-0001 37 mm 11.2 mm 45.8 mm MT5400
Black Bay 58 M7939A1A0NU-0002 39 mm 11.7 mm 47.8 mm MT5400-U
Black Bay 58 18K M79018V-0006 39 mm 12.7 mm 47.8 mm MT5400
Black Bay 58 925 M79010SG-0002 39 mm 12.7 mm 47.8 mm MT5400
Black Bay 58 Bronze M79012M-0001 39 mm 11.9 mm 47.8 mm MT5400
Black Bay 58 GMT M7939G1A0NRU-0001 39 mm 12.8 mm — MT5450-U
Black Bay 68 M7943A1A0NU-0001 43 mm 13.6 mm — MT5601-U
Black Bay Bronze M79250BA-0001 43 mm 14.6 mm 52.7 mm MT5601
Black Bay Chrono M79360N-0014 41 mm 14.4 mm 50 mm MT5813
Black Bay GMT M79830RB-0001 41 mm 14.6 mm 50 mm MT5652
Black Bay Pro M79470-0004 39 mm 14.6 mm 47.2 mm MT5652
Pelagos 39 M25407N-0001 39 mm 11.8–12.2 mm⚠ 47 mm MT5400
Pelagos 42 M25600TB-0001 42 mm 14.3 mm 50 mm MT5612
Pelagos FXD M25717N-0001 42 mm 12.8 mm 52 mm MT5602
Pelagos FXD (bidirectional bezel) M25707B-0001 42 mm 12.8 mm 52 mm MT5602
Pelagos FXD Chrono M25827KN-0001 43 mm 13.2 mm 52 mm MT5813
Pelagos FXD GMT M2542GXX7NU-0002 42 mm 12.7 mm — MT5652-U
Pelagos LHD M25610TNL-0001 42 mm 14.3 mm 50 mm MT5612-LHD
Pelagos Ultra M2543C1A7NU-0001 43 mm 14.5 mm — MT5612-U

← All watches