Lake Ontario Statistics 2026 | Area, Depth, Islands & Key Facts

Where Is Lake Ontario?

Lake Ontario is the smallest by surface area and most easterly of North America’s five Great Lakes, sitting on the international border between Ontario, Canada, to the north and New York State, to the south. The lake discharges into the St. Lawrence River, making it the final basin in the Great Lakes chain before water reaches the Atlantic Ocean, and it connects upstream to Lake Erie via the Niagara River and the Welland Canal. Major urban centers ring its shores, including Toronto, Hamilton, and Oshawa on the Canadian side and Rochester on the American side, making the lake a critical piece of infrastructure for shipping, drinking water, and recreation across the region.

Despite ranking last among the Great Lakes by surface area, Lake Ontario remains the 13th-largest lake in the world, a reminder that even the “smallest” member of this famous freshwater system is enormous by any global standard. As of August 2026, the lake’s federal naming status in the United States has drawn fresh attention, following an executive order renaming it “Lake America” for US federal usage — though the lake continues to be known internationally, and referred to throughout this report, as Lake Ontario. This report covers the lake’s core statistics: its area, depth, and the chain of islands scattered along its eastern shore.

Key Lake Ontario Facts in 2026

Source: Encyclopaedia Britannica “Lake Ontario,” updated August 30, 2026; Wikipedia Lake Ontario entry; WorldAtlas Lake Ontario profile.

Taken together, these figures capture a lake that is modest only in relative terms — smallest among the Great Lakes, yet still large enough to rank among the top 15 lakes on Earth by surface area. Its 7,340-square-mile surface and 802-foot maximum depth place it well ahead of most of the world’s freshwater lakes, even as it trails its four sister Great Lakes in overall scale.

What’s notable in 2026 specifically is the naming development affecting the lake’s US federal designation, a change that applies only to American government usage and does not alter any of the lake’s physical characteristics. Every statistic in this report — area, depth, and island composition — remains identical regardless of which name is used, since the underlying geography, hydrology, and ecology of the lake are entirely unaffected by administrative naming decisions.

Lake Ontario Area and Size Statistics 2026

Source: Encyclopaedia Britannica “Lake Ontario”; Wikipedia Lake Ontario infobox data.

Great Lakes Surface Area Comparison (Approx., Square Miles)
Lake Superior    ████████████████████████████████████████ 31,700
Lake Huron       ███████████████████████████████ 23,000
Lake Michigan    ███████████████████████████ 22,300
Lake Erie        ████████████ 9,910
Lake Ontario     █████████ 7,340

Lake Ontario’s 7,340-square-mile surface makes it the smallest of the five Great Lakes by a meaningful margin, sitting well below Lake Erie’s 9,910 square miles and dramatically smaller than Lake Superior’s 31,700. Its elongated, elliptical shape — 193 miles long but only 53 miles at its widest — gives the lake a distinctive footprint compared to its broader, rounder sister lakes.

The lake’s 24,720-square-mile drainage basin, more than three times its own surface area, funnels water in from the Niagara, Genesee, Oswego, and Black rivers to the south and the Trent River to the north, before all of it exits through the St. Lawrence River. This basin size, combined with the lake’s 712-mile shoreline, underscores how much surrounding geography and hydrology feeds into what is, on paper, the smallest lake in the Great Lakes chain.

Lake Ontario Depth and Volume Statistics 2026

Source: Encyclopaedia Britannica; New World Encyclopedia; Wikipedia Lake Ontario infobox data.

Lake Ontario Depth Profile
Average depth   █████████████████ 283 ft
Maximum depth   ███████████████████████████████████████████████████ 802 ft

The gap between Lake Ontario’s 283-foot average depth and its 802-foot maximum depth at the Rochester Basin shows how uneven the lakebed is beneath a surface that looks relatively uniform from shore. That maximum depth makes it the third-deepest of the five Great Lakes, trailing only Lake Superior and Lake Michigan, even though it ranks last in overall surface area — a reminder that a lake’s footprint and its depth don’t necessarily move together.

Despite exceeding Lake Erie in total water volume at roughly 391 to 393 cubic miles, Lake Ontario still holds the second-smallest volume among the five Great Lakes overall, a function of its comparatively narrow surface area even with genuine depth in places like the Rochester Basin. The six-year water residence time — how long, on average, a given molecule of water spends in the lake before flowing out through the St. Lawrence — reflects its position as the terminal basin in the Great Lakes chain, receiving inflow from the entire upstream system via the Niagara River before finally discharging to the ocean.

Lake Ontario Islands Statistics 2026

Source: Wikipedia Wolfe Island, Amherst Island, Howe Island, and Simcoe Island entries; WorldAtlas Lake Ontario islands overview.

Lake Ontario's Largest Islands by Area (Square Kilometers)
Wolfe Island        ████████████████████████████████████████ 124 km²
Amherst Island      █████████████████████ 66-70 km²
Howe Island         ██████████ 31 km²

Lake Ontario’s islands cluster almost entirely along its northeastern and eastern shores, in the stretch of water between the lake’s outlet at Kingston and the headland of Prince Edward County — the westernmost extension of the famous Thousand Islands region. Wolfe Island, at 124 square kilometers, is by far the largest, roughly 29 kilometers long and home to around 1,400 year-round residents, a population that can double or triple during the summer tourist season. The island sits directly between Kingston, Ontario, and Cape Vincent, New York, and its original Mohawk name, Kawehnóhkwes tsi kawè:note (“Long Island Standing”), was formally restored to local signage in 2021.

Amherst Island, the lake’s second-largest at roughly 66 to 70 square kilometers, along with smaller neighbors like Howe Island and Simcoe Island, together form the township of Frontenac Islands, incorporated in 1998 and home to a combined population of under 2,000 people. All of these islands share a common geological foundation — a basement rock layer found throughout the region — and most are reachable only by ferry, giving them a distinctly quieter, more rural character compared to the dense urban shoreline surrounding Toronto and Rochester. Toronto’s own Toronto Islands, by contrast, function more as an urban park and recreational escape just offshore from Canada’s largest city; readers interested in the broader metropolitan area these islands sit beside can find further detail in our Population of Toronto, Canada statistics report.

Lake Ontario Geological and Ecological Statistics 2026

Source: Lakepedia Lake Ontario profile; WorldAtlas Lake Ontario overview.

Lake Ontario's Place in the Great Lakes Hydrological Chain
Lake Superior → Lake Michigan/Huron → Lake Erie → Lake Ontario → St. Lawrence River → Atlantic Ocean
                                                        ▲
                                                  (final basin)

Lake Ontario’s basin was carved out during the last ice age by the retreating Wisconsin ice sheet, a process that deposited enormous quantities of sediment southward and left behind distinctive landforms like drumlins, kames, and moraines across the surrounding landscape. As the ice sheet retreated northward, it temporarily clogged the outlet of the St. Lawrence Valley, causing the lake to sit at a significantly higher water level during a geological stage known as Lake Iroquois, before eventually draining down to its modern configuration.

Today, the lake’s shoreline supports dense deciduous forests, dominated by oak, maple, basswood, and ash trees, alongside abundant waterfowl populations including Canadian geese that gather along its banks. As the final lake in the Great Lakes hydrological chain, Lake Ontario receives the accumulated outflow of the entire upstream system — Superior, Michigan, Huron, and Erie — before passing that water onward through the St. Lawrence River to the Atlantic Ocean, a role that makes its water levels and quality directly dependent on conditions across the whole Great Lakes basin. Given how closely tied the lake’s islands and shoreline communities are to seasonal weather patterns, readers may find useful context in our Winter Weather statistics for Canada report, which covers the broader climate conditions shaping this region.

Lake Ontario Compared to the Other Great Lakes 2026

Source: US EPA Great Lakes fact sheets; Wikipedia Great Lakes comparative data; Britannica Great Lakes overview.

Great Lakes Maximum Depth Comparison (Feet)
Lake Superior       ███████████████████████████████████████████████████ 1,332
Lake Michigan       █████████████████████████████████████ 923
Lake Ontario        ██████████████████████████████████ 802
Lake Huron          ██████████████████████████ 750
Lake Erie           ███████ 210

Placed alongside its sister lakes, Lake Ontario occupies a distinctive position: smallest by surface area, yet deeper than both Lake Huron and Lake Erie, and only narrowly trailing Lake Michigan for depth. This combination of a compact footprint with genuine depth is part of what makes the lake resistant to the kind of seasonal ice cover that regularly locks up the shallower Lake Erie, since deeper water bodies hold heat more effectively through the winter months.

Population density around the lake also sets it apart: the Golden Horseshoe region on its Canadian shore, anchored by Toronto, Hamilton, and the St. Catharines corridor, accounts for well over half of Ontario’s provincial population living within reach of the shoreline, while the American side remains comparatively rural outside the Rochester metro area. For readers interested in how this urban concentration compares across other major Canadian cities near the Great Lakes system, our Canada population by city statistics report offers a useful comparative breakdown of Toronto, Vancouver, Calgary, and other major population centers.

Disclaimer: This research report is compiled from publicly available sources. While reasonable efforts have been made to ensure accuracy, no representation or warranty, express or implied, is given as to the completeness or reliability of the information. We accept no liability for any errors, omissions, losses, or damages of any kind arising from the use of this report.

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