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Salikh Osmanov
Salikh Osmanov

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How many addresses fit into a Cell?

#tlb #tvm #func #ton

Intro

While developing a smart contract, I needed to store several addresses in persistent storage. At first this looked trivial, but then a simple question came up: how many addresses can I actually fit into a single cell?

Since TON storage is measured in bits and cells, and both storage and message forwarding cost gas, answering this question precisely matters. To do that, we need to look at how addresses are defined and serialized at the TL-b level.

TL-b schemes

All address formats used in TON are defined in block.tlb. The relevant schemes are:

addr_none$00 = MsgAddressExt;

addr_extern$01 len:(## 9) external_address:(bits len)
= MsgAddressExt;

anycast_info$_ depth:(#<= 30) { depth >= 1 }
rewrite_pfx:(bits depth) = Anycast;

addr_std$10 anycast:(Maybe Anycast)
workchain_id:int8 address:bits256 = MsgAddressInt;

addr_var$11 anycast:(Maybe Anycast) addr_len:(## 9)
workchain_id:int32 address:(bits addr_len) = MsgAddressInt;

_ _:MsgAddressInt = MsgAddress;
_ _:MsgAddressExt = MsgAddress;
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Address constructors

There are exactly four address constructors:

  • addr_none
  • addr_extern
  • addr_std
  • addr_var

Theoretical aspects: calculating address size

In this section we calculate exact bit sizes based strictly on the TL-B definitions.

addr_none 

addr_none$00 = MsgAddressExt;
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  • Constructor tag $00 → 2 bits

Exact size: 2 bits

addr_extern 

addr_extern$01 len:(## 9) external_address:(bits len)
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Components:

  • Constructor tag $01 → 2 bits
  • len:(## 9) → 9 bits
  • external_address:(bits len) → len bits, where len ∈ [0, 511]

Exact size formula:

2 + 9 + len = 11 + len bits
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Minimum size: len = 0 → 11 bits

Maximum size: len = 511 → 522 bits

addr_std 

addr_std$10 anycast:(Maybe Anycast) workchain_id:int8 address:bits256
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Breakdown:

  • Constructor tag $10 → 2 bits
  • anycast:(Maybe Anycast)
    • Presence flag → 1 bit
    • If present:
      • depth:(#<=30) → 5 bits
      • rewrite_pfx:(bits depth) → depth bits, where depth ∈ [1, 30]
  • workchain_id:int8 → 8 bits
  • address:bits256 → 256 bits

Exact size formula:

2 + 1 + (anycast ? (5 + depth) : 0) + 8 + 256
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Without anycast (presence bit = 0):

2 + 1 + 8 + 256 = 267 bits
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With anycast, maximum depth = 30:

2 + 1 + (5 + 30) + 8 + 256 = 302 bits
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addr_var 

addr_var$11 anycast:(Maybe Anycast) addr_len:(## 9)
workchain_id:int32 address:(bits addr_len)
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Components:

  • Constructor tag $11 → 2 bits
  • anycast:(Maybe Anycast)
    • Presence flag → 1 bit
    • If present:
    • depth:(#<=30) → 5 bits
    • rewrite_pfx:(bits depth) → depth bits
  • addr_len:(## 9) → 9 bits
  • workchain_id:int32 → 32 bits
  • address:(bits addr_len) → addr_len bits, where addr_len ∈ [0, 511]

Exact size formula:

2 + 1 + (anycast ? (5 + depth) : 0) + 9 + 32 + addr_len
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Without anycast, maximum address length:

2 + 1 + 9 + 32 + 511 = 555 bits
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With anycast, maximum depth = 30 and maximum address length:

2 + 1 + (5 + 30) + 9 + 32 + 511 = 590 bits
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Practical assumptions (what really happens on mainnet)

Anycast is not used

Since TVM version 10, anycast addresses:

  • are not allowed as message destinations,
  • are not allowed in account addresses,
  • are no longer supported by address parsing and rewrite instructions.

In practice, this means the Maybe Anycast flag is always 0, and the Anycast payload is never present.

addr_var is not used

Currently active workchains (masterchain and basechain):

  • use addr_std,
  • use 256-bit account IDs,
  • use small workchain IDs.

addr_var exists for future extensions and is not used in real contracts today.

Practical address sizes

Internal address (addr_std, real usage) 

2 (tag)
+ 1 (anycast flag)
+ 8 (workchain_id)
+ 256 (account_id)
= 267 bits
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Exact size: 267 bits

This size is fixed.

External address (addr_extern, maximum) 

2 (tag)
+ 9 (length)
+ 511 (payload)
= 522 bits
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Summary

  • TON defines four address constructors: addr_none, addr_extern, addr_std, and addr_var.
  • Theoretical address sizes range from 2 bits to 590 bits.
  • On mainnet today:
    • Anycast is unused.
    • addr_var is unused.
    • All internal addresses are addr_std.

As a result, the practical internal address size is fixed and exactly:

➡️ 267 bits

Knowing this exact value is essential when designing compact storage layouts, estimating gas costs, and deciding how many addresses can fit into a single cell.

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