An ACS (Alliance Combat System) attack only works if every participating fleet lands on the target at the same instant — arrive even a few seconds apart and the defender fights each fleet separately instead of facing one combined force. The rule every ACS guide states is simple: the whole group flies at the speed of its slowest fleet. What no guide gives you is the actual number — the exact speed percentage each faster fleet needs to fly at to land together. That's what this calculator solves.
Enter each fleet's origin coordinates, ship and research levels; the calculator finds your slowest fleet automatically, then works out the speed percentage every other fleet needs to arrive at the exact same second. Distance and flight-time formulas are the same verified ones used in our Flight Time Calculator — see our ACS strategy guide for the full mechanics of how alliance combat works.
How ACS fleet synchronization works
Why every fleet must fly at the slowest fleet's speed
ACS combines multiple fleets into one combined attack, but only if they land in the same instant. The mechanism the game uses is speed percentage: every ship type has a base speed, boosted by its drive technology, and the fleet dispatch screen lets you dial that down from 100% to as low as 10%. Because flight time is a fixed function of distance and speed, slowing a fast fleet down to match a slower one's arrival time is just solving that same formula backwards — which is exactly what this calculator automates.
Picking the anchor fleet
The anchor is whichever fleet takes the longest to reach the target flying at 100% — it can't fly any faster, so every other fleet has to slow down to match it. If your combined attack keeps changing which fleet is slowest as people adjust research levels or ship types, re-run the calculator; the anchor isn't always the fleet with the most ships or the farthest distance, it's whichever one has the worst speed-to-distance ratio.
When a fleet is too fast to slow down enough
The in-game speed dial only goes down to 10% — if a fleet is so much faster than the anchor that even 10% speed still gets it there early, slowing down further isn't an option. The fix is launching that fleet later instead of slower, by exactly the time difference the calculator shows, so it still lands at the same moment as everyone else.
Frequently Asked Questions
How do I calculate ACS split times in OGame?
Find the flight time of your slowest participating fleet flying at 100% speed — that's your target arrival time. Then, for every faster fleet, calculate the speed percentage that makes its own flight time match that target. This calculator does both steps automatically once you enter each fleet's coordinates, ship and research levels.
Why did my ACS fleets still arrive at different times even though I used the calculator?
In-game speed is limited to 10% increments, so the calculator rounds each fleet's required speed to the nearest one rather than an exact fractional percentage — the gap this leaves is small when fleets start at similar distances from the target, but can stretch to several minutes when one fleet is much closer or faster than the anchor fleet. It also assumes every fleet launches at exactly the same real-world moment; even a few seconds of difference in when you click "send" will show up in the result.
Can I speed a fleet up beyond 100% to make an ACS work?
No — 100% is always the fastest a fleet can fly, so the slowest fleet in the group sets the ceiling for how fast the whole attack can arrive. There's no way around this except changing which fleets you're combining or improving that fleet's drive technology before the attack.
What if my fleet is too fast even at the lowest speed setting?
If a fleet would still arrive before the target even at 10% speed (the game's minimum), the calculator flags it and tells you how much later to launch it instead — delaying departure is the correct fix in this situation, not trying to slow down further.
Does ACS defense work the same way as ACS attack for timing?
Yes, the underlying speed-synchronization math is identical whether you're combining fleets to attack a target or combining fleets to defend one under incoming attack — only the destination coordinates change, from the enemy's planet to your own.
Why doesn't my in-game arrival time match this calculator exactly?
This calculator uses the standard OGame ruleset distance and flight-time formulas. If your server runs a custom fleet speed factor or altered ship speeds, adjust the server factor dropdown and each fleet's research levels to match your actual server settings.
Ready to coordinate a real alliance attack? ogame.life is a free-to-play OGame server with an active alliance scene.
