Safety Stock & Reorder Point Calculator

import math

def calculate_safety_stock_and_rop(avg_demand, std_demand, avg_lead_time, std_lead_time, z_score):
    """
    Calculate Safety Stock and Reorder Point (ROP) with variable demand & lead time.
    """
    # Combined lead time standard deviation
    lead_time_variance = (avg_lead_time * (std_demand ** 2)) + ((avg_demand ** 2) * (std_lead_time ** 2))
    combined_sigma = math.sqrt(lead_time_variance)
    
    safety_stock = math.ceil(z_score * combined_sigma)
    lead_time_demand = avg_demand * avg_lead_time
    reorder_point = lead_time_demand + safety_stock
    
    return safety_stock, reorder_point

# Inputs
D = 100
sigma_D = 20
L = 9
sigma_L = 2
Z = 1.645

ss, rop = calculate_safety_stock_and_rop(D, sigma_D, L, sigma_L, Z)

print(f"Safety Stock: {ss} units")
print(f"Reorder Point: {rop} units")

function [safety_stock, rop] = calculate_safety_stock(D, sigma_D, L, sigma_L, Z)
    % Calculate Safety Stock and Reorder Point
    lead_time_variance = (L * (sigma_D^2)) + ((D^2) * (sigma_L^2));
    combined_sigma = sqrt(lead_time_variance);
    
    safety_stock = ceil(Z * combined_sigma);
    rop = (D * L) + safety_stock;
end

% Example
D = 100;
sigma_D = 20;
L = 9;
sigma_L = 2;
Z = 1.645;

[ss, rop] = calculate_safety_stock(D, sigma_D, L, sigma_L, Z);
fprintf('Safety Stock: %d units\n', ss);
fprintf('Reorder Point: %d units\n', rop);