Is Kimi K3.1 Pro always more expensive than Claude Sonnet 5?

Based on the tracked database prices, yes — Kimi K3.1 Pro's $4/$20 per million tokens is exactly double Claude Sonnet 5's $2/$10 on both input and output. Note that Moonshot also sells a standard (non-Highspeed) Kimi K3.1 Pro tier at $2/$10, so confirm which variant your workload actually uses.

Which model is cheaper for output-heavy workloads like coding agents?

Claude Sonnet 5 is cheaper for output-heavy workloads, since its $10/M output rate is half of Kimi K3.1 Pro's $20/M. Any workload generating large amounts of text, code, or reasoning tokens will see costs scale faster on Kimi K3.1 Pro at these tracked rates.

How much would 100M input and 30M output tokens cost per month on each model?

Kimi K3.1 Pro totals $1,000/month ($400 input + $600 output), while Claude Sonnet 5 totals $500/month ($200 input + $300 output). That's a $500 monthly gap, with Claude Sonnet 5 costing exactly half as much at this usage level.

Do these two models have similar context windows?

Kimi K3.1 Pro is documented with roughly a 1 million token context window. Claude Sonnet 5's context window is estimated around 500K tokens based on recent Sonnet-generation patterns, but this should be verified against Anthropic's official specs since it wasn't independently confirmed here.

HEAD-TO-HEAD · FLAGSHIP-TIER · VERIFIED OCTOBER 29, 2026

Kimi K3.1 Pro or Claude Sonnet 5 — which is actually cheaper?

Kimi K3.1 Pro and Claude Sonnet 5 both target high-volume production workloads, but their sticker prices sit far apart: $4/M input and $20/M output for Kimi K3.1 Pro versus $2/M input and $10/M output for Claude Sonnet 5 — exactly double across the board.

Spec	Kimi K3.1 Pro	Claude Sonnet 5
Input / 1M tokens	$4.00	$2.00
Output / 1M tokens	$20.00	$10.00
Context window	1M	500K

The output price gap

The output price is where this comparison is decided. Kimi K3.1 Pro charges $20 per million output tokens, twice Claude Sonnet 5's $10 per million. Since output tokens typically cost 3-5x more than input tokens to generate and dominate the bill in reasoning-heavy or long-form generation tasks, this 2x output gap compounds quickly for agentic, coding, or chain-of-thought-heavy workloads where output volume is high relative to input.

Context window

Kimi K3.1 Pro ships with a large context window, with Moonshot's K3.1 line documented at roughly 1,048,576 tokens. Claude Sonnet 5's context window is estimated here at around 500K tokens based on recent Claude Sonnet generations, though exact figures for this specific version should be confirmed against Anthropic's official documentation since naming and specs evolve quickly.

Worked example

At 100M input and 30M output tokens per month: Kimi K3.1 Pro costs (100 x $4) + (30 x $20) = $400 + $600 = $1,000/month. Claude Sonnet 5 costs (100 x $2) + (30 x $10) = $200 + $300 = $500/month. At this usage pattern, Claude Sonnet 5 is exactly half the cost of Kimi K3.1 Pro — a $500/month difference.

Prices from the LLM Price Watch daily tracker, 2026-10-29. Prices change; use the calculator with your own usage for an exact comparison, or see the full price table for every tracked model.