Build a Commission Calculator App With Streamlit

Commission disputes are one of the biggest sources of friction between sales and finance. Reps want to know what they will earn before a deal closes. Finance wants reps to stop asking. A lightweight Streamlit app that lets reps calculate their own estimated commissions solves both problems.

Defining the Commission Plan¶

Most commission plans have a base rate with accelerators above quota. Define the plan as a Python dictionary:

COMMISSION_PLAN = {
    "base_rate": 0.10,           # 10% on deals up to quota
    "accelerator_1": {
        "threshold": 1.0,        # 100-125% of quota
        "cap": 1.25,
        "rate": 0.15,            # 15% accelerator
    },
    "accelerator_2": {
        "threshold": 1.25,       # 125%+ of quota
        "cap": float("inf"),
        "rate": 0.20,            # 20% super-accelerator
    },
    "quarterly_quota": 250000,
}

The Commission Calculation Engine¶

The calculator applies tiered rates based on where the rep stands against quota:

def calculate_commission(deals, quota, plan):
    total_bookings = sum(deals)
    attainment = total_bookings / quota if quota > 0 else 0

    commission = 0.0
    breakdown = []

    # Base commission on bookings up to quota
    base_eligible = min(total_bookings, quota)
    base_comm = base_eligible * plan["base_rate"]
    commission += base_comm
    breakdown.append(("Base (up to quota)", base_eligible, plan["base_rate"], base_comm))

    # Accelerator 1
    if total_bookings > quota:
        tier1_cap = quota * plan["accelerator_1"]["cap"]
        tier1_eligible = min(total_bookings, tier1_cap) - quota
        tier1_comm = tier1_eligible * plan["accelerator_1"]["rate"]
        commission += tier1_comm
        breakdown.append(("Accelerator 1", tier1_eligible, plan["accelerator_1"]["rate"], tier1_comm))

    # Accelerator 2
    tier1_cap = quota * plan["accelerator_1"]["cap"]
    if total_bookings > tier1_cap:
        tier2_eligible = total_bookings - tier1_cap
        tier2_comm = tier2_eligible * plan["accelerator_2"]["rate"]
        commission += tier2_comm
        breakdown.append(("Accelerator 2", tier2_eligible, plan["accelerator_2"]["rate"], tier2_comm))

    return commission, attainment, breakdown

Building the Streamlit Interface¶

The app gives reps a simple form to enter their deals and see commissions instantly:

import streamlit as st

st.set_page_config(page_title="Commission Calculator", page_icon="$")
st.title("Commission Calculator")
st.markdown("Enter your deals to see your estimated commission payout.")

quota = st.number_input(
    "Your Quarterly Quota ($)",
    value=COMMISSION_PLAN["quarterly_quota"],
    step=10000,
)

st.subheader("Enter Your Deals")
num_deals = st.slider("Number of deals", 1, 20, 3)

deals = []
cols = st.columns(3)
for i in range(num_deals):
    with cols[i % 3]:
        amount = st.number_input(
            f"Deal {i + 1} ($)", min_value=0, value=25000, step=5000, key=f"deal_{i}"
        )
        deals.append(amount)

Displaying Results¶

Show the commission breakdown with clear formatting:

if st.button("Calculate Commission"):
    commission, attainment, breakdown = calculate_commission(
        deals, quota, COMMISSION_PLAN
    )

    col1, col2, col3 = st.columns(3)
    col1.metric("Total Bookings", f"${sum(deals):,.0f}")
    col2.metric("Quota Attainment", f"{attainment:.0%}")
    col3.metric("Estimated Commission", f"${commission:,.0f}")

    st.subheader("Commission Breakdown")
    import pandas as pd
    df = pd.DataFrame(breakdown, columns=["Tier", "Eligible Amount", "Rate", "Commission"])
    df["Eligible Amount"] = df["Eligible Amount"].apply(lambda x: f"${x:,.0f}")
    df["Rate"] = df["Rate"].apply(lambda x: f"{x:.0%}")
    df["Commission"] = df["Commission"].apply(lambda x: f"${x:,.0f}")
    st.table(df)

    if attainment >= 1.25:
        st.success("You are in super-accelerator territory!")
    elif attainment >= 1.0:
        st.info("You have hit quota. Accelerators are active.")
    else:
        gap = quota - sum(deals)
        st.warning(f"${gap:,.0f} to go before you hit quota.")

Running the App¶

Launch the calculator with:

streamlit run commission_calculator.py

Share the URL with your sales team. On Streamlit Community Cloud, you can deploy it for free so reps can access it from anywhere without installing Python.

Key Takeaways¶

• A Streamlit commission calculator eliminates back-and-forth between reps and finance about expected payouts
• Defining the comp plan as a configuration dictionary makes it easy to update rates each quarter without rewriting code
• Visual feedback like progress bars and tiered breakdowns help reps understand exactly how accelerators work
• Labeling output as “estimated” avoids disputes while still giving reps the transparency they want