Federal law sets the floor — time and a half after 40 hours in a workweek. A handful of states add daily overtime on top. Here's the map, with official sources.
Under the Fair Labor Standards Act, covered non-exempt employees everywhere in the U.S. earn at least 1.5x their regular rate for hours worked over 40 in a workweek. No federal rule triggers overtime for long days, weekends, or holidays by themselves. The authoritative reference is the U.S. Department of Labor overtime page.
Four states go further and require overtime based on hours in a single day, not just the week:
The most protective rules in the country: generally time and a half after 8 hours in a workday or 40 in a workweek, double time after 12 hours in a day, plus premiums for the seventh consecutive workday.
Official source: California DLSE overtime FAQ →Generally daily overtime after 8 hours in a workday as well as after 40 hours in a workweek, under the Alaska Wage and Hour Act (with exemptions, including some flexible-schedule plans).
Official source: Alaska Wage and Hour Act →Daily overtime after 8 hours in a 24-hour period applies to lower-wage employees (those earning less than 1.5x the state minimum wage); others follow the 40-hour weekly standard.
Official source: Nevada Office of the Labor Commissioner →Overtime is due after 40 hours in a workweek, 12 hours in a workday, or 12 consecutive hours — whichever yields the most pay — under the state COMPS order.
Official source: Colorado Division of Labor Standards & Statistics →Most other states follow the federal weekly standard, though several have industry-specific or situational rules (for example, seventh-day provisions or premium-pay rules for certain retail work in parts of New England). State law also decides things like which employees are exempt and how the “regular rate” is computed for state purposes. Rules change — before making decisions based on a state rule, confirm it with your state's labor department directly.
The rate arithmetic is identical everywhere: time and a half is your rate × 1.5, double time is × 2. State rules only change which hours qualify. Run your numbers with the time and a half calculator, add 2x hours in the overtime calculator if your state provides double time, and note that the federal no-tax-on-overtime deduction only covers FLSA-required overtime — state-only daily overtime generally doesn't qualify.