Geography · Great Lakes · Map
What percentage of Lake Ontario is in Canada? 54.7%
54.7% of Lake Ontario is in Canada: 10,653 of its 19,464 km² of surface. The United States holds 8,810 km² (45.3%). The split is measured along the International Boundary Commission's surveyed border.
- 19,464 km²total surface, 5th-largest of the five Great Lakes
- 54.7%in Canada (10,653 km²), second of five by Canadian share
- 45.3%in the United States (8,810 km²)
- 11.9%of all Great Lakes surface Canada holds (89,664 km²)
Surface area on each side of the surveyed border. Source: International Boundary Commission boundary v1.3; Natural Earth lake outlines; ODC calculation in an equal-area projection (EPSG:3174).
Canada holds 55% of Lake Ontario
Lake Ontario is the smallest Great Lake by surface area (19,464 km²) and the second most Canadian after Huron. It is the lake President Trump's August 27, 2026 order renamed “Lake America” for use inside the United States; Canada holds the larger share. Lake Ontario is also running high: its provisional September 2026 level was 40.4 cm above its 1918–2025 September average (7th-highest of 109 Septembers). Daily readings show the lake falling through late September, so the final monthly figure is likely to come in lower.
All five lakes compared
| Lake | Canada share | Canada km² | U.S. km² | Total km² |
|---|---|---|---|---|
| Superior | 35.8% | 29,460 | 52,851 | 82,311 |
| Michigan | 0.0% | 0 | 57,541 | 57,541 |
| Huron | 61.0% | 36,550 | 23,387 | 59,937 |
| Erie | 50.5% | 13,002 | 12,734 | 25,736 |
| Ontario | 54.7% | 10,653 | 8,810 | 19,464 |
| All five lakes | 36.6% | 89,664 | 155,323 | 244,987 |
Common questions
What percentage of Lake Ontario is in Canada? 54.7%. Canada holds 10,653 of Lake Ontario's 19,464 km² of surface, and the United States holds 8,810 km² (45.3%).
Is Lake Ontario more in Canada or the USA? Canada. It holds 54.7% of the surface to the United States' 45.3%.
How much of Lake Ontario is in the US? 8,810 km², or 45.3% of the lake, on the New York side.
Who owns more of Lake Ontario? Canada, by 1,843 km².
All five lakes on one map: How much of each Great Lake is in Canada?
Other lakes: Lake Superior · Lake Michigan · Lake Huron · Lake Erie