RBE

RBE stands for Red Bloon Equivalent. It is the total amount of damage needed to destroy a bloon and everything that comes out of it, measured in Red Bloons. A Red Bloon has 1 RBE. Any other bloon's RBE is its own outer layer health plus the RBE of all its children. The RBE of a round is simply the RBE of every bloon in it added together.

RBE is the best single number for answering "how strong is this round really?" Two rounds can look similar on screen and be worlds apart in RBE.

How to calculate RBE

The formula is:

RBE = health of the outer layer + RBE of all children

Let's build it up from the bottom.

Regular bloons

• Red: 1 (no children).
• Blue: 1 + Red = 2.
• Green: 1 + Blue = 3.
• Yellow: 1 + Green = 4.
• Pink: 1 + Yellow = 5.
• Black: 1 + two Pinks (5 + 5) = 11.
• White: 1 + two Pinks = 11.
• Purple: 1 + two Pinks = 11.
• Lead: 1 + two Blacks (11 + 11) = 23.
• Zebra: 1 + one Black and one White (11 + 11) = 23.
• Rainbow: 1 + two Zebras (23 + 23) = 47.
• Ceramic: 10 health + two Rainbows (47 + 47) = 104.

MOAB-class bloons

• MOAB: 200 + four Ceramics (4 x 104) = 616.
• BFB: 700 + four MOABs (4 x 616) = 3,164.
• ZOMG: 4,000 + four BFBs (4 x 3,164) = 16,656.
• DDT: 400 + four Camo Regrow Ceramics (4 x 104) = 816.
• BAD: 20,000 + two ZOMGs (2 x 16,656) + three DDTs (3 x 816) = 55,760.

Look at the BAD. Its own shell is 20,000, but the ZOMGs and DDTs inside are worth more than its shell. That is why a defense that "kills the BAD" can still lose to what comes out of it.

Fortified, Camo and Regrow

• Fortified raises RBE. A Fortified Ceramic has 20 health, so 20 + 94 = 114. A Fortified MOAB has 400 health and releases Fortified Ceramics: 400 + (4 x 114) = 856. A Fortified BAD reaches 98,360. See Fortified for the full list.
• Camo does not change RBE. It only changes who can hit the bloon. See Camo.
• Regrow does not change RBE on paper, but layers that grow back have to be popped again, so a slow defense ends up dealing more damage than the RBE says. See Regrow.

Round RBE examples

These are standard round totals:

• Round 28: six Leads = 138 RBE.
• Round 40: one MOAB = 616 RBE.
• Round 46: six Fortified Ceramics = 684 RBE.
• Round 63: 75 Leads and 122 Ceramics = 14,413 RBE.
• Round 80: one ZOMG = 16,656 RBE.
• Round 97: two Fortified ZOMGs = 69,984 RBE.
• Round 98: 30 Fortified BFBs and 8 ZOMGs = 327,456 RBE.

Round 97 shows something important: two Fortified ZOMGs should be 54,592 RBE by the basic formula, but the round is worth 69,984. That is because blimp health starts scaling up after round 80. The same thing makes the round 100 BAD worth 67,200 RBE instead of 55,760. From round 81 onward, regular bloons also release fewer children (a Lead only drops one Black, for example), so freeplay RBE values differ from the table above.

Why RBE matters

Judging a round's difficulty

RBE tells you how much total damage a round needs. A tower setup that clears 15,000 RBE comfortably may struggle on round 63 if it lacks pierce, but it has no chance at all against round 98. Comparing RBE between rounds helps you spot the real spikes.

Cash per round

Early on, each layer you pop pays about one dollar, so early round cash is close to the round's RBE. Round 28's six Leads are 138 RBE and pay $138. Later the game pays less per layer, and blimp health does not pay one dollar per point: round 40's MOAB is 616 RBE but pays $381 from pops. So high RBE means more cash, just not one for one.

Tower mechanics that use RBE

• Bloon Trap and XXXL Trap fill up based on the RBE they capture, as does Obyn Greenfoot's Wall of Trees.
• Great White, Orca and Megalodon can only grab bloons below a certain RBE.
• Benjamin's Trojan stops affected bloons from releasing children, cutting their RBE.
• Defortify effects lower a round's RBE by removing armor.

Common mistakes

• Counting blimps instead of RBE. "Just two blimps" on round 97 is almost 70,000 RBE.
• Ignoring the children. Killing the MOAB layer is only a third of a MOAB's RBE; the four Ceramics are the rest.
• Using pre-80 numbers in freeplay. Blimp health scales after round 80, so late game RBE keeps climbing.

Frequently asked questions

What does RBE mean in BTD6?

Red Bloon Equivalent: the total damage needed to pop a bloon and all of its children, measured in Red Bloons.

What is the RBE of a MOAB?

616: 200 for the MOAB shell plus 104 for each of its four Ceramics. A Fortified MOAB is 856.

What is the RBE of a BAD?

55,760 by the base formula, or 98,360 when Fortified. On round 100 the BAD is worth 67,200 because blimp health scales after round 80.

Does Camo or Regrow change RBE?

No. Only Fortified changes RBE. Regrow can make you deal extra damage in practice because regrown layers have to be popped again.

Is RBE the same as health?

No. Health is just the outer layer. RBE adds the health of everything inside, so a Ceramic has 10 health but 104 RBE.

Can I see a round's RBE in the game?

BTD6 does not show round RBE in-game. Our bloon pages list each bloon's RBE so you can work it out.