It's about 85,000 times as heavy as a Golf Ball
In other words, 0.00000400 megatonnes is 87,090 times the weight of a Golf Ball, and the weight of a Golf Ball is 0.000011480 times that amount.(per R&A USGA Rules of Golf; maximum rule weight)
According to the Rules of Golf (as approved by the United States Golf Association and the Rules Committee of the Royal and Ancient Golf Club of Saint Andrews), golf balls must weigh no more than 0.000000000045930 megatonnes. Golf balls are not required to have the familiar dimpled pattern, but the design has been popular since its invention in 1905 because it reduces drag while increasing lift.
It's about 100,000 times as heavy as a Light Bulb
In other words, 0.00000400 megatonnes is 120,000 times the weight of a Light Bulb, and the weight of a Light Bulb is 0.00000830 times that amount.(a.k.a. lamp) (for A19-size, 60w, incandescent bulb by Bulbrite; package weight)
A standard, sixty-watt light bulb weighs about 0.0000000000340 megatonnes. The tightly-coiled filament inside a bulb of this size would measure about 579mm if uncoiled and stretched out.
It's about 150,000 times as heavy as a Battery (AA)
In other words, the weight of a Battery (AA) is 0.00000590 times 0.00000400 megatonnes.(Alkaline)
An "AA" size battery weighs 0.0000000000240 megatonnes. AA batteries came into common use during World War II and were given their name by the American National Standards Institute (ANSI) Committee C18 because they were smaller than the "A" size batteries which were invented first.
It's about 200,000 times as heavy as a Mouse
In other words, 0.00000400 megatonnes is 190,000 times the weight of a Mouse, and the weight of a Mouse is 0.00000530 times that amount.(a.k.a. "House mouse", Mus musculus) (adult)
The weight of a mouse is typically an average of 0.0000000000210 megatonnes. While most mice typically live two to three years, the Methuselah Mouse Prize — an award administered by a non-profit organization which advances aging-related research — was once awarded to a team of scientists whose research resulted in a mouse living just under five years.
It's about one-two-hundred-thousandth as heavy as The Golden Gate Bridge
In other words, 0.00000400 megatonnes is 0.000004970 times the weight of The Golden Gate Bridge, and the weight of The Golden Gate Bridge is 201,000 times that amount.(San Francisco, California and Marin County, California) (Post 1986 weight reduction; total weight of bridge, anchorage, and approaches)
Following the completion of the 1986 project to eliminate excess material, the total weight of the Golden Gate Bridge — including its anchorages and approaches — is 0.8050 megatonnes. The two main cables in the spanning the bridge are spun out of a total of 129,000 km (80,200 mi) of wire.
It's about 250,000 times as heavy as a Compact disc
It's about 350,000 times as heavy as a Battery (AAA)
In other words, the weight of a Battery (AAA) is 0.00000300 times 0.00000400 megatonnes.(Alkaline)
An "AAA" size battery weighs 0.0000000000120 megatonnes. Batteries are named by the American National Standards Institute (ANSI) Committee C18 and AAA batteries were given their name because they were smaller than the "AA" and "A" size batteries which were invented first.