• Java

<T> int bytes(T t) {
    String s = t.getClass().getSimpleName();
    return switch (s) {
        case "Boolean" -> 1;
        case "Byte" -> Byte.BYTES;
        case "Short" -> Short.BYTES;
        case "Character" -> Character.BYTES;
        case "Integer" -> Integer.BYTES;
        case "Float" -> Float.BYTES;
        case "Long" -> Long.BYTES;
        case "Double" -> Double.BYTES;
        default -> -1;
    };
}

• Ada

N : Integer := (T'Size + 7) / 8;

• C

n = sizeof (t);

• C++

std::size_t n = sizeof(t);

• C#

int n = sizeof(T);

• C#

int n = Marshal.SizeOf(t);

• C#

int n;
unsafe
{
    n = sizeof(T);
}

• D

auto n = T.sizeof;

• Fortran

n = c_sizeof(i)

• Go

var t T
tType := reflect.TypeOf(t)
n := tType.Size()

• Pascal

n := SizeOf(T);

• Perl

use Devel::Size qw(total_size);
my $n = total_size $t;

• Python

n = pympler.asizeof.asizeof(t)

• Python

n = getsizeof(t)

• Ruby

n = ObjectSpace.memsize_of(t)

• Rust

let n = std::mem::size_of::<T>();