Lightning Channel Size Calculator

What is a Lightning Channel?

A Lightning channel is a two-party payment channel built on top of Bitcoin. When you open a channel, you lock Bitcoin into a multisig contract on the Bitcoin blockchain. This creates a private payment lane where you can send and receive instant payments without waiting for block confirmations.

The channel's capacity determines how much you can send and receive. Choosing the right size is important: too small and you'll run out of capacity, too large and you tie up more Bitcoin than necessary.

How to Size Your Channel

A good rule of thumb is to make your channel 2-3x your expected monthly transaction volume. This provides enough headroom for both sending and receiving while accounting for the fact that your balance shifts between local (sendable) and remote (receivable) as you transact.

Key factors to consider:

• Monthly volume: how much you expect to send and receive in total
• Send/receive ratio: whether you mostly send or mostly receive payments
• Opening cost: the on-chain fee to create the channel
• Expected duration: how long you plan to keep the channel open

Understanding Channel Balance

Every Lightning channel has two sides: local balance (what you can send) and remote balance (what you can receive). When you open a channel, all the capacity starts on your local side. As you make payments, balance shifts to the remote side, giving you receiving capacity.

The send/receive ratio slider in the calculator helps you estimate how much capacity you need on each side based on your expected usage pattern.

Frequently Asked Questions

What is the minimum channel size?

The protocol minimum is 20,000 sats, but most implementations recommend at least 100,000 sats for practical use. Channels under 1 million sats may have routing difficulties and high relative fees.

How much does it cost to open a channel?

Opening a channel requires an on-chain Bitcoin transaction (about 140 vBytes). The cost depends on current fee rates: at 10 sat/vB it costs about 1,400 sats, at 50 sat/vB about 7,000 sats. The calculator above shows the exact cost at current rates.

Should I open one big channel or several small ones?

Multiple channels provide better routing options and redundancy. However, each channel has an opening cost. A common approach is to start with 2-3 well-connected channels and add more as needed.

What happens when my channel runs out of capacity?

If you run out of local balance, you can't send. If you run out of remote balance, you can't receive. You can rebalance by circular routing, or close and reopen channels. Some services also offer on-demand liquidity.

Do I need to manage channels with Spark?

No. Spark is a Bitcoin L2 that provides instant payments without channel management. You get Lightning-like speed and fees without worrying about channel sizes, liquidity, or rebalancing.