Which is cheaper, Claude Sonnet 5.5 or DeepSeek V4.1 Flash?

DeepSeek V4.1 Flash is cheaper: $0.30 per million tokens read and $1.20 per million written, against $2 and $10 on Claude Sonnet 5.5. On a mix of 3 tokens read for each 1 written, Claude Sonnet 5.5 costs 7.6 times as much.

Which is better, Claude Sonnet 5.5 or DeepSeek V4.1 Flash?

On the Epoch Capabilities Index, an independent score from Epoch AI that combines over 50 benchmarks, Claude Sonnet 5.5 scores 164 and DeepSeek V4.1 Flash 156, above the top of the range of doubt around DeepSeek V4.1 Flash's score (GPT-5 is 150). One score is an average; test both on your own work before you switch.

What does a support bot cost a month on Claude Sonnet 5.5 and DeepSeek V4.1 Flash?

At 2,000 replies a day, each reading 4,000 tokens (50 percent of them from cache) and writing 300, it costs $432 a month on Claude Sonnet 5.5 and $58.32 on DeepSeek V4.1 Flash: Claude Sonnet 5.5 costs 7.4 times as much for this job.

What does an AI agent task cost on Claude Sonnet 5.5 and DeepSeek V4.1 Flash?

One 40-turn task that reads 2,800,000 tokens in all, 90 percent of them from cache, and writes 40,000, costs $1.21 on Claude Sonnet 5.5 and 15 cents on DeepSeek V4.1 Flash. At 10 tasks a day that is $364 and $44.14 a month.

Which has the larger context window, Claude Sonnet 5.5 or DeepSeek V4.1 Flash?

Neither: both hold 1M tokens at once, about 1,500 pages of English text.

Does the same text take the same number of tokens on Claude Sonnet 5.5 and DeepSeek V4.1 Flash?

No. Our lesson "How AI writes", 1,700 words long, is about 2,100 to 3,600 tokens on Claude Sonnet 5.5 and 2,063 on DeepSeek V4.1 Flash. Each maker cuts text its own way, and every extra token is paid for at the model's price.

Can I pay less on Claude Sonnet 5.5 and DeepSeek V4.1 Flash for work that can wait?

On Claude Sonnet 5.5 only: with a batch, where you collect the answers later, it costs $1 per million tokens read and $5 written. DeepSeek's price page lists no batch price for DeepSeek V4.1 Flash.

Claude Sonnet 5.5 vs DeepSeek V4.1 Flash

DeepSeek V4.1 Flash is the cheaper of the 2: for the same tokens, 3 read for each 1 written, Claude Sonnet 5.5 costs 7.6 times as much. Below are both price lists, what 8 everyday jobs cost a month on each, and how many tokens the same text takes on each, which can change the answer.

Price your own job Compare 2 other models

For the same tokens: DeepSeek V4.1 Flash is cheaper; Claude Sonnet 5.5 costs 7.6 times as much
Cheaper to read: DeepSeek V4.1 Flash, $0.30 against $2
Cheaper to write: DeepSeek V4.1 Flash, $1.20 against $10
Scores higher: Claude Sonnet 5.5, 164 against 156
Larger window: The same, 1M tokens each

Price per million tokens, side by side

In US dollars, as each maker prints them. The better figure in each row is green.

	Claude Sonnet 5.5Anthropic	DeepSeek V4.1 FlashDeepSeek
InputTokens the model reads	$2	$0.30
Cached inputRead again from the cache	$0.10	$0.006
Cache writePutting text in the cache	$2.50	Not listed
OutputTokens it writes, thinking included	$10	$1.20
Blend 3:13 tokens read for each 1 written	$4	$0.525
Batch inputAnswers collected later	$1	Not listed
Batch output	$5	Not listed
Context windowTokens it holds at once	1M	1M
Capability scoreEpoch Capabilities Index; GPT-5 is 150	164	156
Longest answerTokens it writes in 1 reply	128K	Not listed

Read before you choose

DeepSeek V4.1 Flash: The peak-hours price. Off-peak hours are half. Peak is 01:00 to 04:00 and 06:00 to 10:00 UTC on weekdays.

Price changes

Claude Sonnet 5.5: Cached input went from $0.20 to $0.10 per million tokens. The price of a cache write did not change. What changed

The same text, counted by each maker

A price per token means little until you know how many tokens your text is. Here is our lesson How AI writes, about 1,700 words of English, counted the way each maker counts it, and what it costs to send it once.

Claude Sonnet 5.5
about 2,100 to 3,600 tokens
Sent once: 0.41 cents to 0.72 cents at $2 per million
Anthropic does not publish its tokenizer. It says Claude 4.7 and later produce about 30 percent more tokens for the same text than earlier models, and an independent test counted TypeScript at 1.73 times OpenAI's figure. The range runs from OpenAI's count to 1.75 times it.
DeepSeek V4.1 Flash
2,063 tokens
Sent once: 0.062 cents at $0.30 per million
Counted with the tokenizer DeepSeek publishes with V4-Pro and V4.1 Flash, the same models its API serves.

What 8 everyday jobs cost a month on each

Each job at its usual number of runs a day, for 30 days, at the standard price. The cheaper of the 2 is green; open any job in the calculator to change it. Sizes are in tokens, and Claude Sonnet 5.5 can need up to 1.7 times as many as DeepSeek V4.1 Flash for the same words, so its bill for the same work can be up to that much higher.

Job	Claude Sonnet 5.5	DeepSeek V4.1 Flash	Difference
A chat question300 in, 500 out, 100 a day	$16.800.56 cents a run	$2.070.069 cents a run	8.1 times
A hard question, with thinking300 in, 1,400 out, 100 a day	$43.801.5 cents a run	$5.310.18 cents a run	8.2 times
A long report, summarised60,000 in, 2,000 out, 20 a day	$84.0014 cents a run	$12.242 cents a run	6.9 times
A 40-turn agent task2,800,000 in, 40,000 out, 10 a day	$364$1.21 a run	$44.1415 cents a run	8.2 times
A support bot's reply4,000 in, 300 out, 2,000 a day	$4320.72 cents a run	$58.320.097 cents a run	7.4 times
Sort a message into a category250 in, 5 out, 50,000 a day	$8250.055 cents a run	$1220.0081 cents a run	6.8 times
Read an invoice into fields1,500 in, 250 out, 1,000 a day	$1650.55 cents a run	$22.500.075 cents a run	7.3 times
Review a pull request25,000 in, 4,500 out, 50 a day	$1439.5 cents a run	$19.351.3 cents a run	7.4 times

Your own job on both

Start from a job, then set its size, how often it runs and whether the answers can wait. Both bills follow every change.

Start from a job

A short question and a few paragraphs back.

Read in 1 run

tokens

about 230 words

Read again from cache

Instructions or documents the model has read before cost far less the second time.

Written in 1 run, thinking included

tokens

about 380 words

Runs a day

A month of this job

Claude Sonnet 5.5$16.80
0.56 cents a run
DeepSeek V4.1 Flash$2.07
0.069 cents a run

DeepSeek V4.1 Flash saves $14.73 a month; Claude Sonnet 5.5 costs 8.1 times as much.

This job on every model

Why the price per token is only the start

Every maker prints 2 main prices: one for the tokens a model reads (input) and one for the tokens it writes (output). On most current models writing costs 3 to 5 times as much as reading, so which model is cheaper can depend on the job. A job that reads a long document and writes a line pays mostly the input price; a chat that writes paragraphs pays mostly the output price. That is why each comparison prices 8 jobs and not one figure.

The same text is not the same number of tokens on every model. Each maker cuts text its own way, and Anthropic says its models from Claude 4.7 on produce about 30 percent more tokens for the same text than earlier ones. A model with the lower price per token can still send the larger bill, so each comparison counts one of our lessons the way both makers count it.

Discounts change the order too. Work that can wait costs half on a batch at the makers that offer one, and text read again from a cache costs a quarter of the input price or less on every current model here. The price table on each comparison shows who offers what.

Thinking is billed as output, and models differ in how much they think and how long they answer. A price list cannot show that. Before you switch, run the same 10 tasks on both models and compare the bills.

Questions

Which is cheaper, Claude Sonnet 5.5 or DeepSeek V4.1 Flash?: DeepSeek V4.1 Flash is cheaper: $0.30 per million tokens read and $1.20 per million written, against $2 and $10 on Claude Sonnet 5.5. On a mix of 3 tokens read for each 1 written, Claude Sonnet 5.5 costs 7.6 times as much.
Which is better, Claude Sonnet 5.5 or DeepSeek V4.1 Flash?: On the Epoch Capabilities Index, an independent score from Epoch AI that combines over 50 benchmarks, Claude Sonnet 5.5 scores 164 and DeepSeek V4.1 Flash 156, above the top of the range of doubt around DeepSeek V4.1 Flash's score (GPT-5 is 150). One score is an average; test both on your own work before you switch.
What does a support bot cost a month on Claude Sonnet 5.5 and DeepSeek V4.1 Flash?: At 2,000 replies a day, each reading 4,000 tokens (50 percent of them from cache) and writing 300, it costs $432 a month on Claude Sonnet 5.5 and $58.32 on DeepSeek V4.1 Flash: Claude Sonnet 5.5 costs 7.4 times as much for this job.
What does an AI agent task cost on Claude Sonnet 5.5 and DeepSeek V4.1 Flash?: One 40-turn task that reads 2,800,000 tokens in all, 90 percent of them from cache, and writes 40,000, costs $1.21 on Claude Sonnet 5.5 and 15 cents on DeepSeek V4.1 Flash. At 10 tasks a day that is $364 and $44.14 a month.
Which has the larger context window, Claude Sonnet 5.5 or DeepSeek V4.1 Flash?: Neither: both hold 1M tokens at once, about 1,500 pages of English text.
Does the same text take the same number of tokens on Claude Sonnet 5.5 and DeepSeek V4.1 Flash?: No. Our lesson "How AI writes", 1,700 words long, is about 2,100 to 3,600 tokens on Claude Sonnet 5.5 and 2,063 on DeepSeek V4.1 Flash. Each maker cuts text its own way, and every extra token is paid for at the model's price.
Can I pay less on Claude Sonnet 5.5 and DeepSeek V4.1 Flash for work that can wait?: On Claude Sonnet 5.5 only: with a batch, where you collect the answers later, it costs $1 per million tokens read and $5 written. DeepSeek's price page lists no batch price for DeepSeek V4.1 Flash.

Sources