# Limits

> The limits that apply to Cost Explorer reports and forecasts.

## Reports

| Limit                       | Value          |
| --------------------------- | -------------- |
| Length of a report's period | Up to 366 days |
| Groups in one report        | Up to 100,000  |
| Request body size           | Up to 1 MiB    |

Cost Explorer refuses a report with too many groups with `400 Bad Request`. Narrow it with a filter, a
shorter period or a coarser granularity.

## Forecasts

| Limit           | Value                                         |
| --------------- | --------------------------------------------- |
| Forecast period | Starts today or later and ends within 90 days |
| Lookback        | 1 to 90 days, 7 by default                    |
| Granularity     | `daily` or `monthly`                          |

## Concurrent requests

When Cost Explorer is busy, a request waits up to five seconds for its turn. If it is still busy,
it answers `429 Too Many Requests` with `Retry-After: 5`. Wait that long and send the request
again. See [Make API requests](/developer/api#retry-safely).