Free Online Calculators
Quick Answer: Instantly calculate your total sea service in days and months with this free seatime calculator. Enter your vessel name, sign-on, and sign-off dates for each voyage to get a precise record. Perfect for DG Shipping (India), MCA (UK), USCG (USA), and STCW applications. Track multiple voyages, avoid errors, and submit your CoC applications confidently.
Enter the ship name exactly as it appears on your CDC
Use the exact date from your CDC (official joining date)
Use the date on your official sign-off documentation
💡 Tip: Enter your ship name and the dates, then click "Calculate & Add Voyage" to add each trip. Each new trip will be added to the table so you can build your complete sea service record. Your total sea time updates automatically.
Every seafarer's career depends on one critical number — total sea time. Whether you are a deck cadet counting months before your Second Mate CoC exam, an AB tracking days toward an OOW certificate, or a Captain verifying sea service for USCG license renewal, accurate seatime calculation is non-negotiable. One miscalculation means a delayed Certificate of Competency, a rejected application, or a missed career opportunity.
This free seatime calculator online gives you a precise, date-by-date breakdown of sea service across multiple vessels. It works for DG Shipping seatime requirements in India, MCA seatime requirements in the UK, USCG sea time calculations in the USA, and all STCW-compliant administrations worldwide.
A seatime calculator computes the total duration of a seafarer's service on board merchant vessels. You enter the vessel name, joining date, and leaving date for each ship. The calculator adds all service periods and gives your total sea time in months and days — the exact format required by maritime administrations globally.
Seafarers know it by different names depending on their region:
All serve the same purpose — preventing errors in your sea service record that cost you time and career progression.
Using this free seatime calculator takes under two minutes per voyage entry.
Type the ship name exactly as it appears on your Continuous Discharge Certificate (CDC) or sea service letter.
Use the exact date from your CDC. For MCA and DG Shipping use DD/MM/YYYY format. For USCG use MM/DD/YYYY. Never use your travel date to the port — always use your official joining date.
Use the date on your official sign-off documentation. If your CDC shows a different date than your actual departure, always use the CDC date — that is what your administration verifies.
The calculator instantly shows that voyage duration and adds it to your running total. Repeat for every ship you have served on. Your complete sea service record builds automatically in a log table below.
Compare your total against the sea time requirement for the rank or certificate you are applying for. The sections below cover exact requirements for DG Shipping, MCA, and USCG.
The STCW Convention (1978, Manila Amendments 2010) sets the minimum sea time standards all signatory nations follow. Key calculation principles include:
DNS (Diploma in Nautical Science) cadets from IMU-affiliated institutes must complete:
Critical DG Shipping rule: At least half of total required sea service must be on foreign-going or coastal trading vessels of 3,000 GT and above engaged on voyages of 500 nautical miles or more. Additionally, six months of supervised navigational watchkeeping must be completed on such qualifying vessels. Log your vessel GT and trading area for every voyage in your seatime tracker — you will need this information at the MMD office.
The MCA's Sea Service Testimonial (SST) verification system is strict. A poorly documented application causes delays of up to 160 days in issuing your Notice of Eligibility (NoE). Accurate seatime calculation before submission is essential.
MCA calculates watchkeeping service cumulatively. Every 4 hours of watchkeeping performed on a voyage counts as 1 day of watchkeeping service. Time at anchor during an active passage, while the officer maintains a bridge watch, also counts. Your total voyage days and your watchkeeping days are recorded and submitted separately to MCA.
USCG calculation rule: Great Lakes service counts day-for-day up to 100% of total requirement. Inland waters service counts day-for-day for up to 50% of total. STCW-applicable vessel service counts day-for-day regardless of waters.
The Clyde seatime calculator (seatimecalculator.com) was built by Clyde Software for MCA-based sea time calculation. It uses the same join-date to leave-date methodology and remains widely used by UK seafarers. However, it has clear limitations:
This seatime calculator online covers all major administrations — DG Shipping, MCA, and USCG — using the same core calculation logic as the Clyde tool while adding region-specific guidance.
Many seafarers maintain a seatime calculator Excel spreadsheet. It works, but has real risks — date difference formulas break easily, cells get overwritten, and there is no mobile access on board.
An online seatime calculator free tool eliminates formula errors, works on any device including mobile, and gives a clean record ready to verify against official requirements. Best practice: use Excel for ongoing tracking on board, and use this online calculator for final verification before any CoC or license application.
Experienced seafarers follow these habits from their very first contract:
Do not wait until your CoC application. Shipping companies merge, close, or change names — your CDC is your primary evidence but a personal seatime tracker is your backup.
A five-day error can push you below a minimum threshold. Copy dates directly from your CDC.
DG Shipping requires at least half your service on vessels of 3,000 GT and above. Log this for every voyage.
Scan every CDC page and sea service letter. Store them in cloud storage. Multiple seafarers have lost verified sea time to lost documents when applying for Master CoC.
| Rank / Certificate | Administration | Minimum Sea Time |
|---|---|---|
| Deck Cadet (DNS + SSTP) | DG Shipping India | 18 months |
| Deck Cadet (without SSTP) | DG Shipping India | 36 months |
| OOW 3000 GT (cadetship) | MCA UK | 12 months |
| OOW 3000 GT (experienced route) | MCA UK | 36 months |
| AB Unlimited | USCG USA | 1,080 days |
| STCW Able Seafarer Deck | USCG USA | 360 days (with course) |
| Master 100 Ton | USCG USA | 360 days |
| Master 200 GRT | USCG USA | 720 days |
Use this free seatime calculator before every CoC application. Calculate your exact total, verify your qualifying vessel service, and submit with confidence. Never estimate your sea time — always calculate it precisely.