This is a general guide, various factors can affect the range (flat or sloped ground). Knowing the approximate range of shorter can artillery can be helpful when postioning it.
Most Tier VI and above can cover most of the map, some exceptions are noted below.
For shorter range artillery the minimap circles can be used to gauge how far you can shoot and where to position your artillery.
Tier V
For example the Bishop/FV 304/Crusader with the 4.5 inch Howitzer is about the white circle (Range apx 454 meters). Bisope with small gun is yellow circle and a bit.
The leaf blower (105 leFH18B2) is about 4 grids (3.5 diagonally) past the yellow circle (range apx 1000 meters).
AMX 13 AM 5 diagonally past the yellow circle
The Grille large gun is about 3 grids past the yellow circle (small gun yellow circle)
Tier VI - Tier X (Generally range is not an issue - some exceptions are noted)
VI Hummel small gun 2.5 - 3 grid past yellow line
VI FV 304 Big gun White line
Tier VII
Crusader with the 4.5 inch Howitzer is about the white circle (Range apx 454 meters).
Tier VIII
FV 207 QF 6in Mk V 5 grids past the yellow line
Tier X
Conqueror GC is about 3 Grids past the yellow circle
The closest circle shows your current view range (green - apx 300 meters). Any enemy tank inside that circle, will be visible to you and your team mates, unless the tank is behind a rock or building, or if it is inside a bush.
The middle circle shows the maximum view range (white - 454 meters). If you have a good crew, and a tank with good view range, the green and white circle will have the same distance from your tank. (They show almost as one circle.)
The third circle is the max draw (render range - apx 580 meters) the range where tanks spotted by one of your teammates will be visible also to you, even if the tank is outside your view range.
Information is taken from:
WoT 0.8.0 SPG maximum ranges in a horizontal plane:
T1 HMC 3.5 - 4 diagonal grids past yellow
T57 using 76 mm Gun M1918 with 76 mm High-Explosive M48: 518.45m
T57 using 76 mm Gun M1918 with 76 mm High-Explosive Anti-Tank HEAT: 518.45m
SU-18 using 76 mm Howitzer mod. 1927 with 76 mm High-Explosive UOF-354K: 551.72m
SU-18 using 76 mm Howitzer mod. 1927 with 76 mm High-Explosive Anti-Tank BP-354: 551.72m approximately white line
Sturmpanzer I Bison using 15 cm sIG 33 L/11 with 150 mm High-Explosive Sprgr L erz.: 463.46m
Sturmpanzer I Bison using 15 cm sIG 33 L/11 with 150 mm High-Explosive Sprgr L: 463.46m
Sturmpanzer I Bison using 15 cm sIG 33 L/11 with 150 mm High-Explosive Anti-Tank Gr 39 H1A L: 463.46m
RenaultBS using 76 mm Schneider with 76 mm High-Explosive OEO mle. 1917: 450.00m approximately white line
RenaultBS using 76 mm Schneider with 76 mm High-Explosive Anti-Tank OCO mle. 1941: 450.00m
M37 using 105 mm Howitzer M3 with 105 mm High-Explosive HE M1: 437.23m
M37 using 105 mm Howitzer M3 with 105 mm High-Explosive Anti-Tank HEAT M67: 480.96m
M37 using 105 mm Howitzer M4 with 105 mm High-Explosive HE M1: 963.32m
M37 using 105 mm Howitzer M4 with 105 mm High-Explosive Anti-Tank HEAT M67: 1,107.82m
G PZ Mark VI - approximately 3 past the yellow line
Lloyd GC - approximately yellow line
Wespe using 10,5 cm leFH 16 L/22 with 105 mm High-Explosive Sprgr K: 996.25m
Wespe using 10,5 cm leFH 16 L/22 with 105 mm High-Explosive Anti-Tank Gr 39 H1A: 1,006.95m
Wespe using 10,5 cm leFH 18 L/28 with 105 mm High-Explosive Sprgr K: 994.94m
Wespe using 10,5 cm leFH 18 L/28 with 105 mm High-Explosive Anti-Tank Gr 39 H1A: 1,013.37m
Wespe using 10,5 cm leFH 18 L/28 with 105 mm Armor-Piercing Pzgr 39 K: 1,013.37m
Sturmpanzer II using 15 cm sIG 33 L/11 with 150 mm High-Explosive Sprgr L erz.: 463.46m
Sturmpanzer II using 15 cm sIG 33 L/11 with 150 mm High-Explosive Sprgr L: 463.46m
Sturmpanzer II using 15 cm sIG 33 L/11 with 150 mm High-Explosive Anti-Tank Gr 39 H1A L: 463.46m
Renault FT 75 BS
Lorraine39 L AM using Canon de 105 court mle 1935B with 105 mm High-Explosive OE mle. 1920: 770.42m
Lorraine39 L AM using Canon de 105 court mle 1935B with 105 mm High-Explosive Anti-Tank OCO mle. 1936: 780.13m
Lorraine39 L AM using Canon de 105 court mle 1934S with 105 mm High-Explosive OE mle. 1920: 843.75m
Lorraine39 L AM using Canon de 105 court mle 1934S with 105 mm High-Explosive Anti-Tank OCO mle. 1936: 842.11m
SU-26 using 76 mm Howitzer mod. 1927 with 76 mm High-Explosive UOF-354K: 551.72m
SU-26 using 76 mm Howitzer mod. 1927 with 76 mm High-Explosive Anti-Tank BP-354: 551.72m
SU-26 using 76 mm Howitzer mod. 1903/30 with 76 mm High-Explosive UOF-354K: 519.48m
SU-26 using 76 mm Howitzer mod. 1903/30 with 76 mm High-Explosive Anti-Tank BP-354: 519.48m
SU-26 using 122 mm Howitzer mod. 1930 with 122 mm High-Explosive OF420SOMSH: 638.41m
SU-26 using 122 mm Howitzer mod. 1930 with 122 mm High-Explosive OF420SO: 638.41m
SU-26 using 122 mm Howitzer mod. 1930 with 122 mm High-Explosive Anti-Tank BP450SO: 637.59m
105 leFH18B2 using 105 mm leFH18 L28 with 105 mm High-Explosive Sprg K: 1,000.42m
105 leFH18B2 using 105 mm leFH18 L28 with 105 mm High-Explosive Anti-Tank Gr39H1A: 1,018.95m
105 leFH18B2 using 105 mm leFH18 L28 with 105 mm Armor-Piercing PzGr39K: 1,018.95m
SU-5 using 76 mm Howitzer mod. 1903/30 with 76 mm High-Explosive UOF-354K: 519.48m
SU-5 using 76 mm Howitzer mod. 1903/30 with 76 mm High-Explosive Anti-Tank BP-354: 519.48m
SU-5 using 122 mm Howitzer mod. 1930 with 122 mm High-Explosive OF420SOMSH: 638.41m
SU-5 using 122 mm Howitzer mod. 1930 with 122 mm High-Explosive OF420SO: 638.41m
SU-5 using 122 mm Howitzer mod. 1930 with 122 mm High-Explosive Anti-Tank BP450SO: 637.59m
SU-5 using 152 mm Mortar NM mod. 1931 with 152 mm High-Explosive 53-OF500: 605.00m
SU-5 using 152 mm Mortar NM mod. 1931 with 152 mm High-Explosive Anti-Tank 53-BP520: 605.00m
M7 Priest using 105 mm Howitzer M3 with 105 mm High-Explosive HE M1: 380.74m
M7 Priest using 105 mm Howitzer M3 with 105 mm High-Explosive Anti-Tank HEAT M67: 418.81m
M7 Priest using 105 mm Howitzer M2A1 with 105 mm High-Explosive HE M1: 906.96m
M7 Priest using 105 mm Howitzer M2A1 with 105 mm High-Explosive Anti-Tank HEAT M67: 876.85m
T82 approximately yellow plus 3
Grille using 15 cm sIG 33 L/11 with 150 mm High-Explosive Sprgr L erz.: 355.61m
Grille using 15 cm sIG 33 L/11 with 150 mm High-Explosive Sprgr L: 355.61m
Grille using 15 cm sIG 33 L/11 with 150 mm High-Explosive Anti-Tank Gr 39 H1A L: 355.61m
Grille using 15 cm sFH 13 L/17 with 150 mm High-Explosive Sprgr 18: 711.22m
Grille using 15 cm sFH 13 L/17 with 150 mm High-Explosive Anti-Tank Gr 39 H1A: 711.22m
AMX 105AM using Canon de 105 court mle 1934S with 105 mm High-Explosive OE mle. 1920: 843.75m
AMX 105AM using Canon de 105 court mle 1934S with 105 mm High-Explosive Anti-Tank OCO mle. 1936: 842.11m
AMX 105AM using Canon de 105 mle1930 Schneider AM with 105 mm High-Explosive OE mle. 1930: 1,000.00m
AMX 105AM using Canon de 105 mle1930 Schneider AM with 105 mm AP Composite-Rigid FrtPrf1943: 1,000.00m
AMX 13 F3 AM using Obusier de 155 mm C mle.1917 with 155 mm High-Explosive OE mle 1917: 1,102.50m
AMX 13 F3 AM using Obusier de 155 mm C mle.1917 with 155 mm High-Explosive Anti-Tank Gr 39 H1A: 1,210.00m
AMX 13 F3 AM using Canon de 155 mm de 33 calibres with 155 mm High-Explosive 155 OE mle 1956: 1,250.00m
AMX 13 F3 AM using Canon de 155 mm de 33 calibres with 155 mm High-Explosive M 107: 1,250.00m
AMX 13 F3 AM using Canon de 155 mm de 33 calibres with 155 mm High-Explosive Anti-Tank Gr 39 H1A: 1,232.67m
SU-8 using 122 mm Howitzer A-19 with 122 mm High-Explosive UOF-471: 888.35m
SU-8 using 122 mm Howitzer A-19 with 122 mm AP Composite-Rigid UBR-471P: 888.35m
SU-8 using 152 mm Howitzer ML-20 mod. 1931 with 152 mm High-Explosive 53-OF-530: 919.44m
SU-8 using 152 mm Howitzer ML-20 mod. 1931 with 152 mm High-Explosive Anti-Tank 53BP540: 925.36m
Hummel using 15 cm sFH 13 L/17 with 150 mm High-Explosive Sprgr 18: 1,210.00m
Hummel using 15 cm sFH 13 L/17 with 150 mm High-Explosive Anti-Tank Gr 39 H1A: 1,210.00m
Hummel using 15 cm sFH 18 L/30 with 150 mm High-Explosive Sprgr G: 1,263.68m
Hummel using 15 cm sFH 18 L/30 with 150 mm High-Explosive Anti-Tank Gr 39 H1A G: 1,260.00m
M41 using 155 mm Howitzer M1 with 155 mm High-Explosive HE M102: 1,210.00m
M41 using 155 mm Howitzer M1 with 155 mm High-Explosive Anti-Tank HEAT M167: 1,210.00m
M41 using 155 mm Gun M1918M1 with 155 mm High-Explosive HE M101: 1,210.00m
M41 using 155 mm Gun M1918M1 with 155 mm High-Explosive HE M101M2: 1,315.84m
S-51 using 152 mm BR-2 with 152 mm High-Explosive 53-OF551: 1,139.55m
S-51 using 152 mm BR-2 with 152 mm Armor-Piercing 53-G-551: 1,139.55m
S-51 using 152 mm BR-2 with 152 mm High-Explosive 53-OF-551BM: 1,139.55m
S-51 using 203 mm B-4 with 203 mm High-Explosive F-625D: 1,229.09m
S-51 using 203 mm B-4 with 203 mm Armor-Piercing G-620: 1,227.35m
S-51 using 203 mm B-4 with 203 mm High-Explosive F-625DBM: 1,229.09m
M12 using 155 mm Gun M1918M1 with 155 mm High-Explosive HE M101: 1,210.00m
M12 using 155 mm Gun M1918M1 with 155 mm High-Explosive HE M101M2: 1,315.84m
M12 using 155 mm Gun M1A1 with 155 mm High-Explosive HE M101M4: 1,315.84m
M12 using 155 mm Gun M1A1 with 155 mm High-Explosive HE M101M6: 1,315.84m
SU-14 using 152 mm BR-2 with 152 mm High-Explosive 53-OF551: 1,295.85m
SU-14 using 152 mm BR-2 with 152 mm Armor-Piercing 53-G-551: 1,295.85m
SU-14 using 152 mm BR-2 with 152 mm High-Explosive 53-OF-551BM: 1,295.85m
SU-14 using 203 mm B-4 with 203 mm High-Explosive F-625D: 1,210.42m
SU-14 using 203 mm B-4 with 203 mm Armor-Piercing G-620: 1,208.70m
SU-14 using 203 mm B-4 with 203 mm High-Explosive F-625DBM: 1,210.42m
Lorraine155 50 using Canon de 155 mm de 33 calibres with 155 mm High-Explosive 155 OE mle 1956: 1,250.00m
Lorraine155 50 using Canon de 155 mm de 33 calibres with 155 mm High-Explosive M 107: 1,250.00m
Lorraine155 50 using Canon de 155 mm de 33 calibres with 155 mm High-Explosive Anti-Tank Gr 39 H1A: 1,232.67m
Lorraine155 50 using Obusier de 155 mm mle.1950 with 155 mm High-Explosive 155 OE mle 1956: 1,201.78m
Lorraine155 50 using Obusier de 155 mm mle.1950 with 155 mm High-Explosive M 107: 1,201.78m
Lorraine155 50 using Obusier de 155 mm mle.1950 with 155 mm High-Explosive Anti-Tank Gr 39 H1A: 1,204.17m
GW Panther using 15 cm sFH 18 L/30 with 150 mm High-Explosive Sprgr G: 1,263.68m
GW Panther using 15 cm sFH 18 L/30 with 150 mm High-Explosive Anti-Tank Gr 39 H1A G: 1,260.00m
GW Panther using 15 cm sFH 36 L/30 Ausf. 1943 with 150 mm High-Explosive Sprgr G 31: 1,406.98m
GW Panther using 15 cm sFH 36 L/30 Ausf. 1943 with 150 mm High-Explosive Anti-Tank Gr 39H2A G: 1,408.11m
GW Panther using 15 cm sFH 36 L/30 Ausf. 1943 with 150 mm High-Explosive Sprgr 36: 1,406.98m
M40/M43 using 155 mm Gun M1A1 with 155 mm High-Explosive HE M101M4: 1,315.84m
M40/M43 using 155 mm Gun M1A1 with 155 mm High-Explosive HE M101M6: 1,315.84m
M40/M43 using 203 mm Howitzer M1 with 203 mm High-Explosive HE A1M1: 1,178.78m
M40/M43 using 203 mm Howitzer M1 with 203 mm Armor-Piercing M106/M78: 1,178.78m
M40/M43 using 203 mm Howitzer M1 with 203 mm High-Explosive HE M106: 1,178.78m
Lorraine155 51 using Obusier de 155 mm mle.1950 with 155 mm High-Explosive 155 OE mle 1956: 1,201.78m
Lorraine155 51 using Obusier de 155 mm mle.1950 with 155 mm High-Explosive M 107: 1,201.78m
Lorraine155 51 using Obusier de 155 mm mle.1950 with 155 mm High-Explosive Anti-Tank Gr 39 H1A: 1,204.17m
Lorraine155 51 using Canon de 155 mm L GPF with 155 mm High-Explosive OE M101M4: 1,296.00m
Lorraine155 51 using Canon de 155 mm L GPF with 155 mm High-Explosive OE M101M6: 1,296.00m
Lorraine155 51 using Canon de 155 mm L GPF with 155 mm High-Explosive Anti-Tank Gr 39 H1A: 1,275.17m
Object 212 using 152 mm BR-2 with 152 mm High-Explosive 53-OF551: 1,315.84m
Object 212 using 152 mm BR-2 with 152 mm Armor-Piercing 53-G-551: 1,315.84m
Object 212 using 152 mm BR-2 with 152 mm High-Explosive 53-OF-551BM: 1,315.84m
Object 212 using 203 mm B-4 with 203 mm High-Explosive F-625D: 1,229.09m
Object 212 using 203 mm B-4 with 203 mm Armor-Piercing G-620: 1,227.35m
Object 212 using 203 mm B-4 with 203 mm High-Explosive F-625DBM: 1,229.09m
GW Tiger using 17 cm K72 (Sf) with 170 mm High-Explosive Sprgr 18: 1,315.84m
GW Tiger using 17 cm K72 (Sf) with 170 mm High-Explosive Sprg18 Ausf. G: 1,203.91m
GW Tiger using 21 cm Mrs 18/1 (Sf) with 210 mm High-Explosive Gr. 18 Stg: 1,171.62m
GW Tiger using 21 cm Mrs 18/1 (Sf) with 210 mm Armor-Piercing Gr. 18Be: 1,172.28m
GW Tiger using 21 cm Mrs 18/1 (Sf) with 210 mm High-Explosive Gr. 18: 1,171.62m
Object 261 using 180 mm B-1-P with 180 mm High-Explosive F-600D: 1,462.86m
Object 261 using 180 mm B-1-P with 180 mm Armor-Piercing UBR-600: 1,464.49m
Object 261 using 180 mm B-1-P with 180 mm High-Explosive F-600BM: 1,462.86m
Bat Chatillon 155 using Canon de 155 mm with 155 mm High-Explosive OE M101M4: 1,296.00m
Bat Chatillon 155 using Canon de 155 mm with 155 mm High-Explosive OE M101M6: 1,296.00m
Bat Chatillon 155 using Canon de 155 mm with 155 mm High-Explosive Anti-Tank Gr 39 H1A: 1,275.17m
GW Typ E using 21 cm Mörser 18/2 with 210 mm High-Explosive Gr. 18 Stg: 1,171.62m
GW Typ E using 21 cm Mörser 18/2 with 210 mm Armor-Piercing Gr. 18Be: 1,172.28m
GW Typ E using 21 cm Mörser 18/2 with 210 mm High-Explosive Gr. 18: 1,171.62m
T92 using 240 mm Howitzer M1 with 240 mm High-Explosive HE M146: 1,248.44m
T92 using 240 mm Howitzer M1 with 240 mm Armor-Piercing M114/M78: 1,248.44m
T92 using 240 mm Howitzer M1 with 240 mm High-Explosive HE M106: 1,248.44m
Information below taken from:
USA
T57
76 mm Gun (M1918): 520 m
M37
105 mm Howitzer M3: 440 m (480 m HEAT)
105 mm Howitzer M4: 960 m (1100 m HEAT)
M7 Priest
105 mm Howitzer M3: 380 m (420 m HEAT)
105 mm Howitzer M2A1 905 m (875 m HEAT)
M41
155 mm Howitzer M1: 1210 m
155 mm Gun M1918M1: 1210 m (1315 m M101M2)
M12
155 mm Gun M1918M1: 1210 m (1315 m M101M2)
155 mm Gun M1A1: 1315 m
M40/M43
155 mm Gun M1A1: 1315 m
203 mm Howitzer M1: 1175 m
T92
240 mm Howitzer M1: 1250 m
German
Bison
15 cm sIG 33 L/11: 465 m
StPz II
15 cm sIG 33 L/11: 465 m
Wespe
10.5 cm leFH 16 L/22: 1000 m
10.5 cm leFH 18 L/28: 1000 m
Grille
15 cm sIG 33 L/11: 355 m
15 cm sFH 13 L/17: 710 m
Hummel
15 cm sFH 13 L/17: 1210 m
15 cm sFH 18 L/30: 1260 m
GW Panther
15 cm sFH 18 L/30: 1260 m
15 cm sFH 36 L/30 Ausf. 1943: 1400 m
GW Tiger
17 cm K72 (Sf): 1315 m (1200 m Ausf. G)
21 cm Mrs 18/1 (Sf): 1170 m
GW Typ E
21 cm Mörser 18/2: 1170 m
French
Renault BS
76 mm Schneider: 450 m
Lorraine 39 L AM
Canon de 105 court mle 1935B: 775 m
Canon de 105 court mle 1934S: 840 m
105 leFH18B2
105 mm leFH18 L28: 1000 m
AMX 105AM
Canon de 105 court mle 1934S: 845 m
Canon de 105 mle 1930 Schneider AM: 1000 m
AMX 13 F3 AM
Obusier de 155 mm C mle.1917: 1100 m (1210 m H1A)
Canon de 155 mm de 33 calibres: 1250 m
Lorraine 155 50
Obusier de 155 mm C mle.1917: 1250 m
Obusier de 155 mm mle.1950: 1200 m
Lorraine 155 51
Obusier de 155 mm mle.1950: 1200 m
Canon de 155 mm L GPF: 1300 m
Bat Chatillon 155
Canon de 155 mm: 1295 m
Soviet
SU-18
76 mm Howitzer mod. 1927: 550 m
SU-26
76 mm Howitzer mod. 1927: 550 m
76 mm Howitzer mod. 1903/30: 520 m
122 mm Howitzer mod. 1930: 635 m
SU-5
76 mm Howitzer mod. 1903/30: 520 m
122 mm Howitzer mod. 1930: 635 m
152 mm Mortar NM mod. 1931: 600 m
SU-8
122 mm Howitzer A-19: 890 m
152 mm Howitzer ML-20 mod. 1931: 920 m
S-51
152 mm BR-2: 1140 m
203 mm B-4: 1230 m
SU-14
152 mm BR-2: 1295 m
203 mm B-4: 1210 m
Object 212
152 mm BR-2: 1315 m
203 mm B-4: 1225 m
Object 261
180 mm B-1-P: 1460 m