How to Calculate Demurrage Using LFD Data

Demurrage calculation LFD is the foundation of every container cost audit. Whether you are forecasting exposure before a vessel discharges or auditing a carrier invoice after the fact, the math starts in the same place: the Last Free Day. Get that date wrong and every number downstream is wrong. This guide walks through the formula, a worked example at the Port of LA, the tiered rate structures the major carriers actually use, and an Excel approach you can replicate in under five minutes.

The Demurrage Formula Explained

Demurrage accrues in two steps. First, calculate when free time ends. Second, calculate what it costs to overstay it.

Step 1 — Calculate LFD: Discharge Date + Free Days = Last Free Day

Step 2 — Calculate Charges: Days Over LFD × Daily Rate × Number of Containers = Total Demurrage

Free days are defined in the carrier's tariff and begin counting from the discharge date — the date the vessel unloads your container onto the terminal, as recorded by the terminal operating system. Most major carriers count calendar days, including weekends and holidays. A container discharged on Wednesday with 4 free days has an LFD of Saturday, not the following Wednesday. This distinction alone causes more missed LFDs than any other single factor.

For a deeper explanation of how LFDs are assigned and tracked across carriers and terminals, see our complete LFD tracking guide.

Step-by-Step Worked Example: Maersk Container at Port of LA

Here is a realistic scenario. A 40' dry container arrives at APM Terminals Los Angeles on a Maersk vessel. The terminal records the discharge date as March 4, 2026. Maersk's standard import tariff grants 4 calendar free days. The importer picks up the container on March 16, 2026.

LFD calculation: March 4 + 4 days = March 8, 2026

Days over LFD: March 9 through March 16 = 8 charged days

Now apply Maersk's tiered rate structure (per Maersk's January 2026 D&D tariff update):

A flat-rate estimate using $225/day × 8 days would have projected $1,800. The tiered structure adds $500 on top of that on a single container. Scale this to 10 containers and the flat-rate undercount is $5,000 on a single shipment.

How Tiered Rates Work

Every major SSL uses a three-tier escalation structure for import demurrage. Tier 1 covers the first few days over LFD at a base rate. Tier 2 escalates by 40–60%. Tier 3 escalates again, typically to roughly double the Tier 1 rate. The intent is to create financial pressure for prompt container pickup — which is also the basis for FMC guidance requiring that demurrage function as a commercial incentive, not a revenue center.

The following table reflects standard import tariff rates for dry 20' and 40' containers at major US ports as of Q1 2026. Contract rates negotiated in service agreements are typically lower. Reefer premiums apply on top of the rates shown.

CMA CGM's Tier 1 rate of $250/day is the highest among the major carriers listed. But CMA CGM and Maersk both grant only 4 free days, meaning demurrage starts a day earlier than on MSC, Hapag-Lloyd, or ONE shipments. That single free day difference is worth $200–$250 per container when missed. For a port-by-port breakdown of free day windows, see our US port free days comparison.

Excel Template: Columns and Formulas

A well-structured spreadsheet handles the tiered math automatically. Set up the following columns, one row per container:

Column A — Discharge Date: Enter as a date value (e.g., 3/4/2026). Format the column as Date.

Column B — Free Days: Enter the number from the carrier's tariff (e.g., 4). Keep a lookup table on a separate sheet by carrier so you can reference it with VLOOKUP.

Column C — LFD: Formula: =A2+B2. Format as Date. This is the Last Free Day — the final day the container can sit without charge.

Column D — Days Over LFD: Formula: =MAX(0,TODAY()-C2). The MAX prevents negative numbers when a container is still within free time. Replace TODAY() with a specific pickup date if you are calculating a closed invoice.

Column E — Tier 1 Days: Formula: =MIN(D2,4). Caps at 4 because Tier 1 covers days 1–4 over LFD.

Column F — Tier 2 Days: Formula: =MAX(0,MIN(D2,8)-4). Captures days 5–8 over LFD (up to 4 days in Tier 2).

Column G — Tier 3 Days: Formula: =MAX(0,D2-8). Everything beyond day 8 over LFD.

Column H — Total Demurrage Cost: Formula (using Maersk rates as an example): =(E2*225)+(F2*350)+(G2*450). Multiply each tier column by the corresponding daily rate. Store rates in named cells or a rate table so you can update them without editing every formula.

Column I — Container Count: Enter the number of containers under this B/L. Multiply Column H by Column I for the total B/L exposure.

Add conditional formatting to Column C (LFD): highlight cells where LFD is within 2 days of TODAY() in yellow, and past LFD in red. This gives you an at-a-glance priority queue across your entire shipment log without scanning individual rows.

For an interactive version that handles this math without spreadsheet setup, use our online demurrage calculator — enter discharge date, free days, and rate and it calculates LFD and total exposure instantly.

Common Calculation Mistakes

Using vessel arrival instead of discharge date. These can differ by 24–48 hours. A vessel that berths at 11 PM may not begin discharging until the following day. Using arrival inflates your free day count and produces an LFD that is one day too late.

Assuming business days when the tariff says calendar days. This is the most common source of missed LFDs. Unless your tariff explicitly states "business days," assume calendar days. Verify this for every carrier you work with — it is stated in the free time and demurrage section of the published tariff.

Applying a flat rate to a tiered invoice. If you dispute a carrier invoice using flat-rate math and the carrier used tiered rates, your dispute number will be wrong. Always match the rate structure in your calculation to the rate structure in the tariff.

Ignoring the terminal storage clock. Carrier demurrage and terminal storage are independent charges with independent free day windows. The terminal may grant only 4 free days while your carrier grants 5. In that case, terminal storage starts on Day 5, even if you are still within carrier free time. Both invoices arrive separately, from different entities.

Not documenting holds and gate closures. Under the Ocean Shipping Reform Act of 2022 (OSRA) and FMC's 46 CFR Part 545, carriers may not charge demurrage for days when containers were not available for pickup due to terminal gate closures, government holds, or carrier-side restrictions. If you do not document these events in real time, you cannot dispute the charges later. Log every hold notice, every gate closure, and every customs exam notification with timestamps.

Use the Interactive Calculator

The Excel approach above is the right tool for bulk reconciliation and invoice auditing across dozens of containers. For quick per-container estimates — especially when you need to show a client or supervisor a current exposure number right now — the interactive calculator is faster.

Our demurrage calculator takes discharge date, free days, daily rate, and container count and returns LFD, days over LFD, and total charge in real time. It also handles multi-container inputs and shows a visual timeline of free days versus charged days, which is useful when explaining the math to a client unfamiliar with how demurrage accrues.

Both the spreadsheet and the calculator rely on accurate LFD data. If you are managing more than 20 active containers at a time, pulling LFDs manually from eight carrier portals introduces lag and errors that will cost more than the tool to fix. API-based LFD aggregation gives you current data across carriers and terminals in one place, with alert thresholds you can set at 48 and 24 hours before LFD expiry.