public static int fieldSizeInBytes(EllipticCurve curve) throws GeneralSecurityException {
    return (fieldSizeInBits(curve) + 7) / 8;
  }
Returns the size of an element of the field over which the curve is defined.

@param curve must be a prime order elliptic curve
@return the size of an element in bytes.
java_src/src/main/java/com/google/crypto/tink/subtle/EllipticCurves.java