Day three. The quota was gone. My batch job had eaten 10 million tokens overnight.
I didn't see it coming. The prompt looked small. The loop looked harmless. The math was brutal.
Free model quotas feel infinite. They aren't. Token accounting is sneaky. Input tokens count. Output tokens count. Context grows with every message.
So I built a budget calculator. It estimates how long a free quota lasts before you start. No surprises mid-project.
MonkeyCode offers a free model tier with 10M tokens and a free server option. Generous on paper. Finite in practice. The calculator is how I decide whether a free tier survives my project.
Disclosure: This article was prepared as part of MonkeyCode's product outreach.
Why quotas die silently
Every API call has a token price. The price is invisible until you check the meter.
The math has four variables. Tokens per prompt. Messages per hour. Hours per day. Days per week. See the pattern?
Multiply them. Compare to the quota. That's the whole trick.
Most projects skip this step. They discover the limit at the worst moment. A deadline, not a planning session.
The calculator
Here's the script I run before touching a free model API. It takes your usage pattern and returns a verdict.
"""
budget_calculator.py — estimate how long a free token quota lasts.
Usage:
python budget_calculator.py
"""
# --- Your inputs ---
QUOTA_TOKENS = 10_000_000 # free tier allowance
# Per-call estimates
AVG_INPUT_TOKENS = 500 # prompt + system message
AVG_OUTPUT_TOKENS = 200 # generated reply
CONTEXT_OVERHEAD = 0.15 # 15% extra for formatting, roles, etc.
# Usage pattern
CALLS_PER_DAY = 200
ACTIVE_DAYS_PER_WEEK = 5
# --- Calculation ---
tokens_per_call = (AVG_INPUT_TOKENS + AVG_OUTPUT_TOKENS) * (1 + CONTEXT_OVERHEAD)
tokens_per_day = tokens_per_call * CALLS_PER_DAY
tokens_per_week = tokens_per_day * ACTIVE_DAYS_PER_WEEK
days_until_exhausted = QUOTA_TOKENS / tokens_per_day
weeks_until_exhausted = QUOTA_TOKENS / tokens_per_week
print(f"Tokens per call: {tokens_per_call:,.0f}")
print(f"Tokens per day: {tokens_per_day:,.0f}")
print(f"Tokens per week: {tokens_per_week:,.0f}")
print()
print(f"Quota: {QUOTA_TOKENS:,.0f}")
print(f"Days until exhausted: {days_until_exhausted:.1f}")
print(f"Weeks (5-day week): {weeks_until_exhausted:.1f}")
print()
if days_until_exhausted < 7:
print("Verdict: TOO TIGHT — you will run out in under a week.")
elif days_until_exhausted < 30:
print("Verdict: RISKY — plan for throttling or a fallback.")
else:
print("Verdict: COMFORTABLE — the quota should last the project.")
Run it with your numbers:
python budget_calculator.py
The script prints a verdict. Three outcomes. Too tight. Risky. Comfortable.
Where the estimates come from
The hardest part is estimating tokens per call. Here's my method.
Run your real prompt once. Check the usage field in the API response. Most providers return prompt_tokens and completion_tokens. Why guess when the API tells you?
Do this for five different prompts. Take the average. Add 15% for context growth.
That's your AVG_INPUT_TOKENS. That's your AVG_OUTPUT_TOKENS.
The 15% overhead covers system prompts, role markers, and formatting. It's a fudge factor. It's better than being wrong by 30%.
A real scenario
Let me walk through a concrete case. A background job that summarizes support tickets.
- Input: 800 tokens per ticket
- Output: 150 tokens per summary
- Volume: 300 tickets per day
- Workdays: 5 per week
tokens_per_call = (800 + 150) * 1.15 # 1,092
tokens_per_day = 1092 * 300 # 327,600
tokens_per_week = 327600 * 5 # 1,638,000
Ten million divided by 327,600. That's 30.5 days. Six weeks of workdays.
That's comfortable. The quota survives the project with room to spare.
A second scenario
Now a chat assistant. Users send messages. The conversation grows.
- Input: 2,000 tokens per turn (conversation history)
- Output: 300 tokens per reply
- Users: 50 per day
- Turns per user: 10
tokens_per_call = (2000 + 300) * 1.15 # 2,645
tokens_per_day = 2645 * 500 # 1,322,500
tokens_per_week = 1322500 * 7 # 9,257,500
Ten million divided by 1,322,500. That's 7.5 days.
A week and a half. The quota dies before the project ships.
The difference is conversation history. Every turn re-sends the whole context. Tokens compound fast.
The compounding problem
Chat is the quota killer. Each turn includes all previous turns.
Turn 1: 500 tokens. Turn 2: 800. Turn 10: 3,500. The cost grows linearly with conversation length.
Your average is not your peak. A long conversation can burn 10x your average call.
The calculator uses averages. Real usage has spikes. Plan for the spikes. How long before your chat app burns the whole quota?
How to stretch the quota
If the verdict says risky, you have options.
Reduce context. Summarize old messages. Drop system prompts. Keep the conversation lean.
Cache responses. Identical questions get identical answers. A cache layer cuts calls dramatically.
Batch work. Process tickets in one prompt instead of one per call. Fewer calls, more tokens each.
Cap conversation length. After 10 turns, summarize and restart. The user loses memory, but the quota survives. Worth the tradeoff?
The free server factor
MonkeyCode's free server option is the second half of the equation. The token allowance is the first half. The calculator budgets the allowance.
The server matters because it's where the tokens get spent. A free endpoint means no per-call billing. The quota is the only meter.
That's the tradeoff. Finite tokens, no invoice. The calculator tells you how finite.
Decision table
| Workload | Typical quota life | Verdict |
|---|---|---|
| One-off script | Months | Comfortable |
| Batch summarization | 4-6 weeks | Comfortable |
| Semantic cache + misses | 2-4 weeks | Risky |
| Chat assistant, 50 users | 1-2 weeks | Too tight |
| High-volume RAG pipeline | Days | Too tight |
Limitations
This calculator is an estimate. Real usage varies. Tokenizers differ between models.
Free quotas change without notice. The published terms at the time of writing matter. Re-check before you rely on it.
The calculator measures quantity, not quality. A free quota of 10M tokens is worthless if the model answers poorly. Evaluate quality separately.
Who should skip this
If your project is a weekend prototype, skip the math. The quota will outlast your interest.
If your project is a production service, skip the free tier. You need an SLA, not a quota.
If your usage is tiny and unpredictable, just start. The calculator is for projects with a known shape.
Your turn
Run the calculator on your own project. Post your numbers in the comments.
I want to see your verdict. Comfortable, risky, or too tight?
Top comments (0)