kcalc: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/kcalc - from package: kdeutils

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/kcalc - from package: kcalc

You may install the required package with command apt-get install {package}

Error in other languages:
kcalc: bevel nie gevind nie
kcalc: comandă negăsită
kcalc: comando não encontrado
kcalc: commande introuvable
kcalc: command not found
kcalc: käsku ei ole
kcalc: không tìm thấy lệnh
kcalc: komanda nerasta
kcalc: Kommando nicht gefunden.
kcalc: kommandot finns inte
kcalc: komut yok
kcalc: nie znaleziono polecenia
kcalc: níor aimsíodh an t-ordú
kcalc: no se encontró la orden
kcalc: no s'ha trobat l'ordre
kcalc: opdracht niet gevonden
kcalc: parancs nem található
kcalc: perintah tidak ditemukan
kcalc: príkaz nenájdený
kcalc: příkaz nenalezen
kcalc: команда не найдена
kcalc: командата не е открита
kcalc: 命令找不到
kcalc: コマンドが見つかりません