Surface Interval Calculator: Check Time Between Dives

What the current tool calculates

Enter the actual end date and time of the last dive, then the planned start date and time of the next. The result is the available surface time, shown in hours and minutes. The next start must be after the previous end; incomplete or invalid entries produce a validation message.

Use the same local time basis for both entries and check the dates when an interval crosses midnight. This is a time calculation. The form does not take depth, bottom time, breathing gas, previous dive history or your computer model as calculation inputs.

Why repetitive-dive planning needs more than a clock

A diver can retain inert gas after surfacing. Repetitive-dive procedures account for prior exposure and the next planned profile, using the approved method you are trained to follow. Two divers with the same surface time can have different histories and planning limits.

A longer interval alone does not establish readiness. Review the next profile using your own dive computer or verified agency tables, including relevant gas and repetitive-dive procedures. Confirm the plan with the professional leading the dive.

What the readiness checklist means

The checklist asks you to confirm that your computer or tables have been checked, that nobody has possible diving-injury symptoms, and that the profile, gas, conditions, buddy plan and emergency procedures have been reviewed.

Ticking a box records your acknowledgement; it does not measure physiology or independently verify the statement. A completed checklist is not an automated go decision. Live conditions and the divers in front of you still matter.

Limits and disabled calculations

This page does not calculate decompression status, residual nitrogen or pressure-group transitions. The tools collection has a separate Dive Tables planner for table-based calculations. Its current metric-air bundle is enabled; other gas and unit bundles remain unavailable where their reference data is incomplete. Read the planner notices and use only the table system you are trained to follow.

Scuba Steve does not override your dive computer, certified training, agency tables or local professional judgement. If the tool output conflicts with an approved planning method, stop and resolve the discrepancy with qualified help before diving.

Flying and other plans after diving

This elapsed-time tool does not calculate no-fly clearance. Follow the guidance appropriate to your dive history, training and computer, and seek qualified advice where needed. Travel deadlines do not change the requirements of the planning method you use.

If anyone has possible diving-injury symptoms, do not plan another dive around a timer. Follow your emergency plan, provide oxygen if trained and equipped, and contact emergency services or appropriate diving-medical support.

Use the result as one part of preparation

For example, entering a last-dive end of 10:00 and a next start of 11:30 on the same date gives 1 hour 30 minutes. The result describes the gap; it does not approve any depth, duration or breathing gas for the next dive.

Use the trip planner to organise your schedule and operator questions, and the tools index to find other available checks. Keep the authoritative repetitive-dive assessment with the computer, tables and procedures you are trained to use.

Frequently asked questions